Tag Archives: Popular Physics

Gravitational Machines [CL]

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http://arxiv.org/abs/2305.10470


A gravitational machine is defined as an arrangement of gravitating masses from which useful energy can be extracted. It is shown that such machines may exist if the masses are of normal astronomical size. A simple example of a gravitational machine, consisting of a double star with smaller masses orbiting around it, is described. It is shown that an efficient gravitational machine will also be an emitter of gravitational radiation. The emitted radiation sets a limit on the possible performance of gravitational machines, and also provides us with a possible means for detecting such machines if they exist.

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F. Dyson
Fri, 19 May 23
34/46

Comments: 4 pages, one figure

Black Holes as the source of the dark energy: a stringent test with the high-redshift JWST AGNs [CEA]

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http://arxiv.org/abs/2305.03408


It has been suggested that there is evidence for cosmological coupling of black holes (BHs) with an index of $k\approx 3$ and hence the BHs serve as the astrophysical source of the dark energy. The data sample however is limited for the redshifts $\leq 2.5$. Recently, the James Webb Space Telescope (JWST) has detected more than 180 high-redshift Active Galactic Nuclei (AGNs) and quasars. Among the JWST NIRSpec/NIRCam resolved AGNs, three are identified in early-type host galaxies with a redshift $z\sim 4.5-7$. Their $M_{\star}$ and $M_{\rm BH}$, however, are in tension with the prediction of the cosmological coupling of black holes with $k=3$ at a confidence level of $\sim 3\sigma$, which is not in support of the hypothesis that BHs serve as the origin of dark energy. The future observations of high-redshift AGNs by JWST will further test such a hypothesis by identifying more early-type host galaxies in the higher mass range.

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L. Lei, L. Zu, G. Yuan, et. al.
Mon, 8 May 23
40/63

Comments: 9 pages, 3 figures, 1 table; Submitted to ApJL. Comments are welcome!

Anomalies in Gravitational-Lensed Images Revealing Einstein Rings Modulated by Wavelike Dark Matter [CEA]

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http://arxiv.org/abs/2304.09895


Elucidating the nature of Dark Matter (DM), which does not interact with light and which interacts with known matter primarily or only through gravity, is one of the principal quests in physics. Leading candidates for DM are weakly interacting massive particles (WIMPs) or ultralight bosons (axions), at opposite extremes in mass scales, that have been postulated by competing theories to solve deficiencies in the Standard Model of particle physics. Whereas DM WIMPs behave like discrete particles ($\varrho$DM), quantum interference between DM axions is manifested as waves ($\psi$DM). Here, we show that gravitational lensing leaves signatures in multiply-lensed images of background galaxies that reveal whether the foreground lensing galaxy inhabits a $\varrho$DM or $\psi$DM halo. Whereas $\varrho$DM lens models leave well documented anomalies between the predicted and observed brightnesses and positions of multiply-lensed images, $\psi$DM lens models correctly predict the level of anomalies left over by $\varrho$DM lens models. More challengingly, when subjected to a battery of tests for reproducing the quadruply-lensed triplet images in the system HS 0810+2554, $\psi$DM is able to reproduce all aspects of this system whereas $\varrho$DM often fails. The growing success of $\psi$DM in reproducing astrophysical observations tilt the balance toward new physics invoking axions.

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A. Amruth, T. Broadhurst, J. Lim, et. al.
Fri, 21 Apr 23
56/60

Comments: This preprint has not undergone peer review or any post-submission improvements or corrections. The Version of Record of this article is published in Nature Astronomy, and is available online at this https URL or this https URL Please check out the final version on Nature Astronomy’s website for the improved main text

The Breakthrough Listen Search for Intelligent Life: Nearby Stars' Close Encounters with the Brightest Earth Transmissions [SSA]

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http://arxiv.org/abs/2304.07400


After having left the heliosphere, Voyager 1 and Voyager 2 continue to travel through interstellar space. The Pioneer 10, Pioneer 11, and New Horizons spacecraft are also on paths to pass the heliopause. These spacecraft have communicated with the Deep Station Network (DSN) radio antennas in order to download scientific data and telemetry data. Outward transmissions from DSN travel to the spacecraft and beyond into interstellar space. These transmissions have encountered and will encounter other stars, introducing the possibility that intelligent life in other solar systems will encounter our terrestrial transmissions. We use the beamwidth of the transmissions between DSN and interstellar spacecraft to perform a search around the past and future positions of each spacecraft obtained from the JPL Horizons System. By performing this search over the Gaia Catalogue of Nearby Stars (GCNS), a catalogue of precisely mapped stars within 100 pc, we determine which stars the transmissions of these spacecraft will encounter. We highlight stars that are in the background of DSN transmissions and calculate the dates of these encounters to determine the time and place for potential intelligent extraterrestrial life to encounter terrestrial transmissions.

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R. Derrick and H. Isaacson
Tue, 18 Apr 23
5/80

Comments: N/A

The most fundamental question of all times [CEA]

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http://arxiv.org/abs/2304.01011


In the last few decades, reading the literature, we realized that we Astronomers have a strong preference to undertake very ambitious projects, and search for answers to the most fundamental questions in the history of the entire Universe. After running multiple times into such cardinal quest, the curiosity became no more sustainable and we had to find out. To our greater surprise, in the last few decades we had been restlessly participating to this superhuman endevour. Therefore we hereby explore the roots and grounds of this fundamental search, through the past decades, centuries and millennia.

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S. Berta, A. Poisson, K. Scherz, et. al.
Tue, 4 Apr 23
29/111

Comments: April fools!

Can AI Put Gamma-Ray Astrophysicists Out of a Job? [CL]

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http://arxiv.org/abs/2303.17853


In what will likely be a litany of generative-model-themed arXiv submissions celebrating April the 1st, we evaluate the capacity of state-of-the-art transformer models to create a paper detailing the detection of a Pulsar Wind Nebula with a non-existent Imaging Atmospheric Cherenkov Telescope (IACT) Array. We do this to evaluate the ability of such models to interpret astronomical observations and sources based on language information alone, and to assess potential means by which fraudulently generated scientific papers could be identified during peer review (given that reliable generative model watermarking has yet to be deployed for these tools). We conclude that our jobs as astronomers are safe for the time being. From this point on, prompts given to ChatGPT and Stable Diffusion are shown in orange, text generated by ChatGPT is shown in black, whereas analysis by the (human) authors is in blue.

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S. Spencer, V. Joshi and A. Mitchell
Mon, 3 Apr 23
22/53

Comments: N/A

MO0NFALL: The Great Filter and Exo-Moon Occurrence [EPA]

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http://arxiv.org/abs/2303.18227


We observe neither life beyond Earth, nor moons around exoplanets, despite the prevalence of Earth-like planets across the galaxy. We suggest Moonfall as a possible mechanism to explain both simultaneously.

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C. Brinkman, K. Gootkin, R. Lee, et. al.
Mon, 3 Apr 23
28/53

Comments: N/A

Protoplanet Express, a video game based on numerical simulations [CL]

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http://arxiv.org/abs/2303.17654


Astronomical images can be fascinating to the general public, but the interaction is typically limited to contemplation. Numerical simulations of astronomical systems do permit a closer interaction, but are generally unknown outside the research community. We are developing “Protoplanet Express”, a video game based on hydrodynamical simulations of protoplanetary discs. In the game, the player visits several discs, finds its relevant features and learns about them. Here we present the current version of the game, discuss its reception, and consider its further development.

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J. Cuadra, M. Vergara, B. Escárate, et. al.
Mon, 3 Apr 23
40/53

Comments: 6 pages, 4 figures, submitted to the Proceedings of ASP 2022. Beta version of game available at this https URL

ChatGPT scores a bad birdie in counting gravitational-wave chirps [HEAP]

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http://arxiv.org/abs/2303.17628


How many gravitational-wave observations from compact object mergers have we seen to date? This seemingly simple question has a surprisingly complex answer that even ChatGPT struggles to answer. To shed light on this, we present a database with the literature’s answers to this question. We find values spanning 67-100 for the number of detections from double compact object mergers to date, emphasizing that the exact number of detections is uncertain and depends on the chosen data analysis pipeline and underlying assumptions. We also review the number of gravitational-wave detections expected in the coming decades with future observing runs, finding values up to millions of detections per year in the era of Cosmic Explorer and Einstein Telescope. We present a publicly available code to visualize the detection numbers, highlighting the exponential growth in gravitational-wave observations in the coming decades and the exciting prospects of gravitational-wave astrophysics. See this http URL We plan to keep this database up-to-date and welcome comments and suggestions for additional references.

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F. Broekgaarden
Mon, 3 Apr 23
52/53

Comments: 1 April submission, with fun videos for visualizing the landscape of gravitational waves! (they are awesome!) See this http URL

When Tails Tell Tales [SSA]

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http://arxiv.org/abs/2303.16941


The enigmatic open clusters serve as a constant reminder of the mysteries of the universe, helping to confront astronomical theories. Unknown to many, these clusters often possess tails with inappropriate labels, serving as the tell-tale signs of their historical journey. But unlike typical tails, these extensions can either precede or follow the body, yet they consistently unfold a cosmic mystery to be solved. I present a succinct survey of this subject matter, detailing the intrepid efforts of astronomers who have dared to challenge our knowledge about these creatures, and offer a novel proposal for their nomenclature, while not disregarding the philosophical ramifications.

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H. Boffin
Fri, 31 Mar 23
38/70

Comments: The Astronomical Enquirer – Other articles in this journal are available at this https URL

Galaxy Evolution in $\ddotμ$ based Cosmologies [GA]

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http://arxiv.org/abs/2303.17002


We present the first study of galaxy evolution in $\ddot{\mu}$ based cosmologies. We find that recent JWST observations of massive galaxies at extremely high redshifts are consistent with such a cosmology. However, the low redshift Universe is entirely divergent from the $\ddot{\mu}$ cosmic star formation rate density. We thus propose that our Universe was at one point dominated by a Primordial Bovine Herd (PBH) which later decayed producing dark energy. Note that we do not detail the mechanisms by which this decay process takes place. Despite its vanishingly small probability for existence, a $\ddot{\mu}$ based cosmological model marries the disparate findings in the high and low redshift Universe.

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W. Roper, S. Wilkins, S. Riggs, et. al.
Fri, 31 Mar 23
55/70

Comments: N/A

I Murdered Conan O'Brien and Nobody Will Ever Know — an exercise in inference sabotage [HEAP]

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http://arxiv.org/abs/2303.17400


I employ an optimization-based inference methodology together with an Ising model, in an intentionally ineffectual manner, to get away with murdering an obstreperous scientific collaborator. The antics of this collaborator, hereafter “Conan O’Brien,” were impeding the publication of an important manuscript. With my tenure date looming, I found myself desperate. Luckily, I study inference, a computational means to find a solution to a physical problem, based on available measurements (say, a dead body) and a dynamical model assumed to give rise to those measurements (a murderer). If the measurements are insufficient and/or the model is incomplete, one obtains multiple “degenerate” solutions to the problem. Degenerate solutions are all equally valid given the information available, and thus render meaningless the notion of one “correct” solution. Typically in scientific research, degeneracy is undesirable. Here I describe the opposite situation: a quest to create degenerate solutions in which to cloak myself. Or even better: to render measurements incompatible with a solution in which I am the murderer. Moreover, I show how one may sabotage an inference procedure to commit an untraceable crime. I sit here now, typing victoriously, a free woman. Because you won’t believe me anyway. And even if you do, you’ll never prove a thing.

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E. Armstrong
Fri, 31 Mar 23
57/70

Comments: 10 pages, 3 figures, 2 tables

As a matter of colon: I am NOT digging cheeky titles (no, but actually yes :>) [IMA]

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http://arxiv.org/abs/2303.17059


What’s in a name, a poet once asked. To which we present this work, where we investigate the importance of a paper title in ensuring its best outcome. We queried astronomy papers using NASA ADS and ranked 6000 of them in terms of cheekiness level. We investigate the correlation between citation counts and (i) the presence of a colon, and (ii) cheekiness ranking. We conclude that colon matters in the anatomy of a paper title. So does trying to be cheeky, but we find that too much cheekiness can lead to cringefests. Striking the right balance is therefore crucial. May we recommend aiming for a level 4 cheekiness on a scale of 1-5.

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J. Tan and T. Suk
Fri, 31 Mar 23
61/70

Comments: 4 pages, 4 figures, 1 meme. Submitted to Acta Prima Aprila

UFOs: Just Hot Air or Something Meteor? [CL]

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http://arxiv.org/abs/2303.17103


For much of February 2023, the world was in panic as repeated balloon-like unidentified flying objects (UFOs) were reported over numerous countries by governments that often responded with military action. As a result, most of these craft either escaped or were destroyed, making any further observation of them nearly impossible. These were not the first time balloon-like objects have loomed over Earth, nor are they likely to be the last. This has prompted us to push for a better understanding of UFOs. First we demonstrate that the distribution of balloon incidents and other UFO reports are consistent with being drawn from the same geographic distribution, and further that both of these distributions are consistent with the areas of the Earth that feature the jet stream. Second we show that there are more UFO sightings during meteor showers, as we would expect if meteor showers, already a known source of extraterrestrial material, are being used to provide some manner of distraction to help alien craft enter the Earth’s atmosphere without drawing undue attention. These links between alleged balloon incidents, UFO reports, and meteor showers establish a transport pipeline for alien craft from interplanetary and possibly interstellar space to the Earth’s surface.

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M. Lund
Fri, 31 Mar 23
68/70

Comments: 9 pages, 4 figures, 2 tables, submission for Saturday’s Acta Prima Aprilia

Inferring the rate of technosignatures from sixty years of nondetection [CL]

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http://arxiv.org/abs/2301.07165


For about the last 60 years the search for extraterrestrial intelligence has been monitoring the sky for evidence of remotely detectable technological life beyond Earth, with no positive results to date. While the lack of detection can be attributed to the highly incomplete sampling of the search space, technological emissions may be actually rare enough that we are living in a time when none cross the Earth. This possibility has been considered in the past, but not to quantitatively assess its consequences on the galactic population of technoemissions. Here we derive the likelihood of the Earth not being crossed by signals for at least 60 years to infer upper bounds on their rate of emission. We found less than about one to five emissions per century generated from the Milky Way (95 % credible level), implying optimistic waiting times until the next crossing event of no less than 60 to 1,800 years with a 50 % probability. A significant fraction of highly directional signals increases the emission rates upper bounds, but without systematically changing the waiting time. Our results provide a benchmark for assessing the lack of detection and may serve as a basis to form optimal strategies for the search for extraterrestrial intelligence.

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C. Grimaldi
Thu, 19 Jan 23
12/100

Comments: 8 pages, 4 figures

Resurfaced 1964 VRT video interview of Georges Lemaître [CL]

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http://arxiv.org/abs/2301.07198


On December 31 2022, the Vlaamse Radio- en Televisieomroeporganisatie (VRT), the national public-service broadcaster for the Flemish Community of Belgium, recovered a video recording of a 1964 interview of Georges Lema\^itre. Up until now, that footage was thought to have been lost. This footage represents a unique insight into the views of the physicist often coined as the “father of the Big Bang”. The interview was conducted in French and is available online with Flemish subtitles. In an effort to make this treasure broadly available, we provide in this paper some brief context, an English translation of the interview as well as the French transcript for reference.

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S. Gontcho, J. Eluo and P. Gabor
Thu, 19 Jan 23
56/100

Comments: VRT article linking the recovered footage: this https URL

Nonprofit Adopt a Star: Lessons from 15 years of Crowdfunding [CL]

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http://arxiv.org/abs/2301.05598


In the past 15 years, the number of known planets outside of our solar system has grown from about 200 to more than 5000. During that time, we have conducted one of the longest crowdfunding campaigns in history, a nonprofit adopt a star program that supports astronomy research. The program includes the targets of NASA space telescopes that are searching for planets around other stars, and it uses the proceeds to help determine the properties of those stars and their planetary systems. I summarize how this innovative program has evolved over the years and engaged the public worldwide to support an international team of astronomers.

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T. Metcalfe
Mon, 16 Jan 23
4/50

Comments: 4 pages, 2 figures. Project website is at this https URL

Nonprofit Adopt a Star: Lessons from 15 years of Crowdfunding [CL]

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http://arxiv.org/abs/2301.05598


In the past 15 years, the number of known planets outside of our solar system has grown from about 200 to more than 5000. During that time, we have conducted one of the longest crowdfunding campaigns in history, a nonprofit adopt a star program that supports astronomy research. The program includes the targets of NASA space telescopes that are searching for planets around other stars, and it uses the proceeds to help determine the properties of those stars and their planetary systems. I summarize how this innovative program has evolved over the years and engaged the public worldwide to support an international team of astronomers.

Read this paper on arXiv…

T. Metcalfe
Mon, 16 Jan 23
14/50

Comments: 4 pages, 2 figures. Project website is at this https URL

Search for Transient, Monochromatic Light from the Galactic Plane [IMA]

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http://arxiv.org/abs/2301.01230


The Galactic Plane was searched for transient, monochromatic light at optical and near-IR wavelengths to detect pulses shorter than 1 sec. An objective-prism Schmidt telescope and CMOS camera were used to observe 973 square degrees along the Galactic Plane within a strip 2.1 deg wide. The non-detections of laser pulses from the Galactic Plane add to the non-detections from more than 5000 stars. The absence of extraterrestrial beacons reveals more of a SETI desert at optical and radio wavelengths.

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G. Marcy and N. Tellis
Wed, 4 Jan 23
22/43

Comments: 24 pages

The Fermi Paradox revisited: Technosignatures and the Contact Era [CL]

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http://arxiv.org/abs/2211.16505


A new solution to the Fermi Paradox is presented: probes or visits from putative alien civilizations have a very low probability until a civilization reaches a certain age (called the Contact Era) after the onset of radio communications. If biotic planets are common, putative advanced civilizations may preferentially send probes to planets with technosignatures, such as radio broadcastings. The contact probability is defined as the chance to find a nearby civilization located close enough so that it could have detected the earliest radio emissions (the radiosphere) and sent a probe that would reach the Solar System at present. It is found that the current contact probability for Earth is very low unless civilizations are extremely abundant. Since the radiosphere expands with time, so does the contact probability. The Contact Era is defined as the time (since the onset of radio transmissions) at which the contact probability becomes of order unity. At that time alien probes (or messages) become more likely. Unless civilizations are highly abundant, the Contact Era is shown to be of the order of a few hundred to a few thousand years and may be applied not only to physical probes but also to transmissions (i.e. SETI). Consequently, it is shown that civilizations are unlikely to be able to inter-communicate unless their communicative lifetime is at least a few thousand years.

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A. Wandel
Thu, 1 Dec 22
13/85

Comments: 12 pages, 5 figures, accepted for publication in the Astrophysical Journal

The enduring mystery of the solar corona [CL]

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http://arxiv.org/abs/2211.17098


Physicists have long known that the Sun’s magnetic fields make its corona much hotter than the surface of the star itself. But how — and why — those fields transport and deposit their energy is still a mystery, as Philip G Judge explains

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P. Judge
Thu, 1 Dec 22
62/85

Comments: N/A

Centenary of Alexander Friedmann's Prediction of the Universe Expansion and the Quantum Vacuum [CL]

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http://arxiv.org/abs/2211.17101


We review the main scientific pictures of the universe developed from ancient times to Albert Einstein and underline that all of them treated the universe as a stationary system with unchanged physical properties. In contrast to this, 100 years ago Alexander Friedmann predicted that the universe expands starting from the point of infinitely large energy density. We briefly discuss the physical meaning of this prediction and its experimental confirmation consisting of the discovery of redshift in the spectra of remote galaxies and relic radiation. After mentioning the horizon problem in the theory of the hot universe, the inflationary model is considered in connection with the concept of quantum vacuum as an alternative to the inflaton field. The accelerated expansion of the universe is discussed as powered by the cosmological constant originating from the quantum vacuum. The conclusion is made that since Alexander Friedmann’s prediction of the universe expansion radically altered our picture of the world in comparison with the previous epochs, his name should be put on a par with the names of Ptolemy and Copernicus.

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G. Klimchitskaya and V. Mostepanenko
Thu, 1 Dec 22
63/85

Comments: 16 pages, 1 figure

Unidentified aerial phenomena II. Evaluation of UAP properties [CL]

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http://arxiv.org/abs/2211.17085


NASA commissioned a research team to study Unidentified Aerial Phenomena (UAP), observations of events that cannot scientifically be identified as known natural phenomena. The Main Astronomical Observatory of NAS of Ukraine conducts an independent study of UAP also. For UAP observations, we used two meteor stations installed in Kyiv and in the Vinarivka village in the south of the Kyiv region. Two-side monitoring of the daytime sky led to the detection of two luminous objects at an altitude of 620 and 1130 km, moving at a speed of 256 and 78 km/s. Colorimetric analysis showed that the objects are dark: B – V = 1.35, V – R = 0.23. The size of objects is estimated to be more than 100 meters. The detection of these objects is an experimental fact. Estimates of their characteristics follow from observational data. The authors do not interpret these objects. Daytime sky monitoring in Kyiv with multi-color DSLR camera at a rate of 30 frames per second in August and September 2018 and in Vinarivka with a multi-color CMOS camera in October 2022 revealed several cases of dark objects (phantoms). The time of their existence is, as a rule, a fraction of a second. These are oval-shaped objects ranging in size from 20 to 100 meters with speeds from 2 to 30 km/s.

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B. Zhilyaev, V. Petukhov and V. Reshetnyk
Thu, 1 Dec 22
76/85

Comments: 13 pages,34 figures, Kinematics and Physics of Celestial Bodies

Galactic settlement of low-mass stars as a resolution to the Fermi paradox [CL]

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http://arxiv.org/abs/2210.10656


An expanding civilization could rapidly spread through the galaxy, so the absence of extraterrestrial settlement in the solar system implies that such expansionist civilizations do not exist. This argument, often referred to as the Fermi paradox, typically assumes that expansion would proceed uniformly through the galaxy, but not all stellar types may be equally useful for a long-lived civilization. We suggest that low-mass stars, and K-dwarf stars in particular, would be ideal migration locations for civilizations that originate in a G-dwarf system. We use a modified form of the Drake Equation to show that expansion across all low-mass stars could be accomplished in 2 Gyr, which includes waiting time between expansion waves to allow for a close approach of a suitable destination star. This would require interstellar travel capabilities of no more than ~0.3 ly to settle all M-dwarfs and ~2 ly to settle all K-dwarfs. Even more rapid expansion could occur within 2 Myr, with travel requirements of ~10 ly to settle all M-dwarfs and ~50 ly to settle all K-dwarfs. The search for technosignatures in exoplanetary systems can help to place constraints on the presence of such a “low-mass Galactic Club” in the galaxy today.

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J. Haqq-Misra and T. Fauchez
Thu, 20 Oct 22
49/74

Comments: Accepted by the Astronomical Journal

Exploration of M31 via Black-Hole Slingshots and the "Intergalactic Imperative" [CL]

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http://arxiv.org/abs/2210.10622


I show that a gravitational slingshot using a stellar-mass black hole (BH) orbiting SgrA* could launch robotic spacecraft toward M31 at $0.1\,c$, a speed that is ultimately limited by the tensile strength of steel and the BH mass, here conservatively estimated as $m_{\rm bh}=5\,M_\odot$. The BH encounter must be accurate to $\lesssim 1\,$km, despite the fact that the BH is dark. Navigation guided by gravitational microlensing can easily achieve this. Deceleration into M31 would rely on a similar engagement (but in reverse) with an orbiting BH near the M31 center. Similarly for a return trip, if necessary. Colonization of M31 planets on 50 Myr timescales is therefore feasible provided that reconstruction of humans, trans-humans, or androids from digital data becomes feasible in the next few Myr. The implications for Fermi’s Paradox (FP) are discussed. FP is restated in a more challenging form. The possibility of intergalactic colonization on timescales much shorter than the age of Earth significantly tightens FP. It can thereby impact our approach to astrobiology on few-decade timescales. I suggest using a network of tight white-dwarf-binary “hubs” as the backbone of a $0.002\,c$ intra-Galactic transport system, which would enable complete exploration of the Milky Way (hence full measurement of all non-zero terms in the Drake equation) on 10 Myr timescales. Such a survey would reveal the reality and/or severity of an “intergalactic imperative”.

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A. Gould
Thu, 20 Oct 22
50/74

Comments: 24 pages, 1 figure

The Inferred Abundance of Interstellar Objects of Technological Origin [CL]

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http://arxiv.org/abs/2209.11262


The local detection rate of interstellar objects can allow for estimations of the total number of similar objects bound by the Milky Way thin disk. If interstellar objects of artificial origin are discovered, the estimated total number of objects can be lower by a factor of about $10^{16}$ if they target the habitable zone around the Sun. We propose a model for calculating the quantity of natural or artificial interstellar objects of interest based on the object’s velocity and observed density. We then apply the model to the case of chemically propelled rockets from extraterrestrial civilizations. Finally, we apply the model to three previously discovered interstellar objects — the object ‘Oumuamua of unknown origin and the first interstellar meteors CNEOS 2014-01-08 and CNEOS 2017-03-09.

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C. Ezell and A. Loeb
Wed, 28 Sep 22
1/89

Comments: 11 pages, 2 figures; submitted for publication

Opportunities for Technosignature Science in the Planetary Science and Astrobiology Decadal Survey [IMA]

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http://arxiv.org/abs/2209.11685


Solar system exploration provides numerous possibilities for advancing technosignature science. The search for life in the solar system includes missions designed to search for evidence of biosignatures on other planetary bodies, but many missions could also attempt to search for and constrain the presence of technology within the solar system. Technosignatures and biosignatures represent complementary approaches toward searching for evidence of life in our solar neighborhood, and beyond. This report summarizes the potential technosignature opportunities within ongoing solar system exploration and the recommendations of the “Origins, Worlds, and Life” Planetary Science and Astrobiology Decadal Survey. We discuss opportunities for constraining the prevalence of technosignatures within the solar system using current or future missions at negligible additional cost, and we present a preliminary assessment of gaps that may exist in the search for technosignatures within the solar system.

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J. Haqq-Misra, R. Ashtari, J. Benford, et. al.
Mon, 26 Sep 22
3/62

Comments: A report from the First Penn State SETI Symposium

Constraints on extragalactic transmitters via Breakthrough Listen [HEAP]

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http://arxiv.org/abs/2209.08147


The Breakthrough Listen Initiative has embarked on a comprehensive SETI survey of nearby stars in the Milky Way that is vastly superior to previous efforts as measured by a wide range of different metrics. SETI surveys traditionally ignore the fact that they are sensitive to many background objects, in addition to the foreground target star. In order to better appreciate and exploit the presence of extragalactic objects in the field of view, the Aladin sky atlas and NED were employed to make a rudimentary census of extragalactic objects that were serendipitously observed with the 100-m Greenbank telescope observing at 1.1-1.9 GHz. For 469 target fields (assuming a FWHM radial field-of-view of 4.2 arcminutes), NED identified a grand total of 143024 extragalactic objects, including various astrophysical exotica e.g. AGN of various types, radio galaxies, interacting galaxies, and one confirmed gravitational lens system. Several nearby galaxies, galaxy groups and galaxy clusters are identified, permitting the parameter space probed by SETI surveys to be significantly extended. Constraints are placed on the luminosity function of potential extraterrestrial transmitters assuming it follows a simple power law and limits on the prevalence of very powerful extraterrestrial transmitters associated with these vast stellar systems are also determined. It is demonstrated that the recent Breakthrough Listen Initiative, and indeed many previous SETI radio surveys, place stronger limits on the prevalence of extraterrestrial intelligence in the distant Universe than is often fully appreciated.

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M. Garrett and A. Siemion
Tue, 20 Sep 22
77/81

Comments: 9 Pages, 5 figures, accepted by MNRAS

How to delay death and look further into the future if you fall into a black hole [CL]

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http://arxiv.org/abs/2209.04823


In this note, we present a pedagogical illustration of peculiar properties of motion in the vicinity and inside black holes. We discuss how a momentary impulse can modify the lifetime of an object radially falling into a Schwarzschild black hole down to singularity. The well known upper limit for a proper time spent within a horizon, in fact, requires an infinitely powerful kick. We calculate the proper time interval (perceived as personal lifetime of a falling observer) till the contact with the singularity, as well as the time interval in the Lema\^itre frame (which reflects how far into the future of the outer world a falling observer can look), for different values of the kick received by the falling body. We discuss the ideal strategy to increase both time intervals by the engine with a finite power.
This example is suitable for university seminars for undergraduate students specializing in General Relativity and related astrophysical subjects.

Read this paper on arXiv…

A. Toporensky and S. Popov
Tue, 13 Sep 22
6/85

Comments: 13 pages with 2 figures, accepted for publication in Resonance

Unidentified aerial phenomena I. Observations of events [IMA]

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http://arxiv.org/abs/2208.11215


NASA commissioned a research team to study Unidentified Aerial Phenomena (UAP), observations of events that cannot scientifically be identified as known natural phenomena. The Main Astronomical Observatory of NAS of Ukraine conducts an independent study of UAP also. For UAP observations, we used two meteor stations. Observations were performed with colour video cameras in the daytime sky. We have developed a special observation technique, for detecting and evaluating UAP characteristics. According to our data, there are two types of UAP, which we conventionally call: (1) Cosmics, and (2) Phantoms. We note that Cosmics are luminous objects, brighter than the background of the sky. Phantoms are dark objects, with contrast from several to about 50 per cent. We observe a significant number of objects whose nature is not clear. Flights of single, group and squadrons of the ships were detected, moving at speeds from 3 to 15 degrees per second. Some bright objects exhibit regular brightness variability in the range of 10 – 20 Hz. We use colourimetry methods to determine of distance to objects and evaluate their colour characteristics. Objects RGB colours of the Adobe colour system had converted to the Johnson BVR astronomical colour system using the colour corrections. Phantom shows the colour characteristics inherent in an object with zero albedos. It is a completely black body that does not emit and absorbs all the radiation falling on it. We see an object because it shields radiation due to Rayleigh scattering. An object contrast makes it possible to estimate the distance using colourimetric methods. Phantoms are observed in the troposphere at distances up to 10 – 12 km. We estimate their size from 3 to 12 meters and speeds up to 15 km/s.

Read this paper on arXiv…

B. Zhilyaev, V. Petukhov and V. Reshetnyk
Thu, 25 Aug 22
29/43

Comments: 8 pages, 23 figures, Advances in Astronomy and Space Physics

The Pedagogical Representation of Mass Functions with LEGO and their Origin [CL]

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http://arxiv.org/abs/2106.10342


We promote the teaching of mass functions as an integral part of an interdisciplinary science education. Mass functions characterize the frequency distributions of objects with different masses on all cosmic scales. We intend to enhance experiential learning of this concept with a creative LEGO brick experiment for a diverse student audience. To our surprise, the LEGO mass function is not only qualitatively but also quantitatively comparable to mass functions found across the Universe. We also discuss the relation between gravitation and mass distributions as a possible explanation for the continuity of the universal mass function.

Read this paper on arXiv…

S. Kautsch, D. Veras and K. Hansotia
Tue, 16 Aug 22
65/74

Comments: This is the version of the article before peer review and submission. The published version is Kautsch, Veras, & Hansotia 2021, European Journal of Physics, 42, 035605, this https URL

Nucleosynthesis in the Cosmos: What we think we know and forthcoming questions [CL]

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http://arxiv.org/abs/2208.05518


We present what we know on nucleosynthesis in the Universe and hypotheses that have been made in this regard. A brief description of the Universe’s evolution during its different stages is offered, indicating which are the periods and mechanisms of element formation. A critical prospective on future research is formulated to validate, modify, or reject the hypotheses formulated. These will involve joint observations that encompass finer measurements of cosmic background radiation, galaxy clusters, and gravitational waves produced by neutron star collisions. The information thus obtained will be combined with restrictions given by theoretical models. Perhaps many current doubts will be clarified, but new questions will arise.

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S. Uribarri and J. Cervantes-Cota
Fri, 12 Aug 22
11/48

Comments: 26 pages, 10 figures. Title and abstract also in Spanish

Evidencing the interaction between science fiction enthusiasm and career aspirations in the UK astronomy community [IMA]

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http://arxiv.org/abs/2208.05825


The anecdotal connection between an interest in science fiction and career aspirations in astrophysics is well established. However strong statistical evidence for such a connection, and a quantitative assessment of its prevalence, has been missing. Here I report the results of two surveys examining the connection between science fiction enthusiasm and astronomical careers – first a case study of the University of Warwick Astronomy and Astrophysics group, carried out in February 2021, and second a larger survey of attendees at the UK National Astronomy Meeting in July 2022. In both surveys, a significant majority of respondents expressed an interest in science fiction. In the larger survey, 93% of UK astronomers (223 of 239 respondents) expressed an interest in science fiction, while 69% (164) stated that it had influenced their life or career choices. This study provides strong statistical evidence for the role of science fiction in influencing the adoption of astronomical careers.

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E. Stanway
Fri, 12 Aug 22
15/48

Comments: 7 pages, 5 figures. Comments welcome

Magnitudes, distance moduli, bolometric corrections, and so much more [IMA]

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http://arxiv.org/abs/2206.00989


This pedagogical document about stellar photometry – aimed at those for whom astronomical arcana seem arcane – endeavours to explain the concepts of magnitudes, color indices, absolute magnitudes, distance moduli, extinctions, attenuations, color excesses, K corrections, and bolometric corrections. I include some discussion of observational technique, and some discussion of epistemology, but the primary focus here is on the theoretical or interpretive connections between the observational astronomical quantities and the physical properties of the observational targets.

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D. Hogg
Fri, 3 Jun 22
12/57

Comments: Not submitted anywhere (yet)

Searching for technosignatures in exoplanetary systems with current and future missions [EPA]

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http://arxiv.org/abs/2206.00030


Technosignatures refer to observational manifestations of technology that could be detected through astronomical means. Most previous searches for technosignatures have focused on searches for radio signals, but many current and future observing facilities could also constrain the prevalence of some non-radio technosignatures. This search could thus benefit from broader participation by the astronomical community, as contributions to technosignature science can also take the form of negative results that provide statistically meaningful quantitative upper limits on the presence of a signal. This paper provides a synthesis of the recommendations of the 2020 TechnoClimes workshop, which was an online event intended to develop a research agenda to prioritize and guide future theoretical and observational studies technosignatures. The paper provides a high-level overview of the use of current and future missions to detect exoplanetary technosignatures at ultraviolet, optical, or infrared wavelengths, which specifically focuses on the detectability of atmospheric technosignatures, artificial surface modifications, optical beacons, space engineering and megastructures, and interstellar flight. This overview does not derive any new quantitative detection limits but is intended to provide additional science justification for the use of current and planned observing facilities as well as to inspire astronomers conducting such observations to consider the relevance of their ongoing observations to technosignature science. This synthesis also identifies possible technology gaps with the ability of current and planned missions to search for technosignatures, which suggests the need to consider technosignature science cases in the design of future mission concepts.

Read this paper on arXiv…

J. Haqq-Misra, E. Schwieterman, H. Socas-Navarro, et. al.
Thu, 2 Jun 22
12/57

Comments: Accepted for publication in Acta Astronautica

Impact of Economic Constraints on the Projected Timeframe for Human-Crewed Deep Space Exploration [CL]

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http://arxiv.org/abs/2205.08061


Deep space exploration offers the most profound opportunity for the expansion of humanity and our understanding of the Universe, but remains extremely challenging. Progress will continue to be paced by uncrewed missions followed up by crewed missions to ever further destinations. Major space powers continue to invest in crewed deep space exploration as an important national strategy. An improved model based on previous work is developed, which projects the earliest possible launch dates for human-crewed missions from cis-lunar space to selected destinations in the Solar System and beyond based on NASA’s historic budget trend and overall development trends of deep space exploration research. The purpose of the analysis is to provide a projected timeframe for crewed missions beyond Mars. Our findings suggest the first human missions from a spacefaring nation or international collaboration to the Asteroid Belt and Jovian System could be scheduled as soon as ~2071 to ~2087 and ~2101 to ~2121, respectively, while a launch to the Saturn System may occur by the year ~2132, with an uncertainty window of ~2129 to ~2153.

Read this paper on arXiv…

P. Rosen, D. Zhang, J. Jiang, et. al.
Wed, 18 May 22
10/66

Comments: 10 pages, 5 figures

Mathematical encoding within multi-resonant planetary systems as SETI beacons [EPA]

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http://arxiv.org/abs/2204.14259


How might an advanced alien civilization manipulate the orbits within a planetary system to create a durable signpost that communicates its existence? While it is still debated whether such a purposeful advertisement would be prudent and wise, we propose that mean-motion resonances between neighboring planets — with orbital periods that form integer ratios — could in principle be used to encode simple sequences that one would not expect to form in nature. In this Letter we build four multi-resonant planetary systems and test their long-term orbital stability. The four systems each contain 6 or 7 planets and consist of: (i) consecutive integers from 1 to 6; (ii) prime numbers from 2 to 11; (iii) the Fibonacci sequence from 1 to 13; and (iv) the Lazy Caterer sequence from 1 to 16. We built each system using N-body simulations with artificial migration forces. We evaluated the stability of each system over the full 10 Gyr integration of the Sun’s main sequence phase. We then tested the stability of these systems for an additional 10 Gyr, during and after post-main sequence evolution of the central stars (assumed to be Sun-like) to their final, white dwarf phase. The only system that was destabilized was the consecutive integer sequence (system i). The other three sequences therefore represent potential SETI beacons.

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M. Clement, S. Raymond, D. Veras, et. al.
Mon, 2 May 22
9/52

Comments: 6 pages, 2 figures, 1 table, accepted for publication in MRNAS

Anthropic constraint on transient variations of fundamental constants [CL]

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http://arxiv.org/abs/2202.04228


The anthropic principle implies that life can emerge and be sustained only in a narrow range of values of fundamental constants (FCs). We extend the anthropic arguments to a regime of transient variations of FCs. Such regime is characteristic of clumpy dark matter models where inside the clumps FCs can reach values vastly different from their everyday values. We show that the passage of such a macroscopic clump through Earth would make Earth uninhabitable. The periodic table of elements is truncated and water fails to serve as a universal solvent. Anthropic principle enables us to improve existing astrophysical bounds on certain dark matter model couplings by five orders of magnitude.

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V. Dergachev, H. Tan, S. Varganov, et. al.
Mon, 25 Apr 22
31/36

Comments: 16 pages, 14 figures

Infrared and Optical Detectability of Dyson Spheres at White Dwarf Stars [SSA]

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http://arxiv.org/abs/2204.09627


It has been hypothesized that advanced technological civilizations will construct giant space colonies and supporting infrastructures to orbit about their home stars. With data from recent satellites that operate at infrared and optical wavelengths (Spitzer, WISE, TESS, Kepler), in company with a few modest assumptions, it is now possible to begin to constrain observationally the frequency of such space-based civilizations in our Milky Way Galaxy.

Read this paper on arXiv…

B. Zuckerman
Thu, 21 Apr 22
52/73

Comments: Accepted for MNRAS

Engineering an Interstellar Communications Network by Deploying Relay Probes [CL]

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http://arxiv.org/abs/2204.08296


We develop a model for an interstellar communication network that is composed of relay nodes that transmit diffraction-limited beams of photons. We provide a multi-dimensional rationale for such a network of communication in lieu of interstellar beacons. We derive a theoretical expression for the bit rate of communication based on fundamental physics, constrained by the energy available for photons and the diffraction of the beam that dilutes the information by the inverse square law. We find that meter-scale probes are severely limited in their bit rate, under 1 Gbps, over distances of a light year. However, that bit rate is proportional to the 4th power of the size of the optics that transmit and receive the photons, and inversely proportional to the square of the distance between them, thus favoring large optics and short separations between nodes. The optimized architecture of interstellar communication consists of a network of nodes separated by sub-light-year distances and strung out between neighboring stars.

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J. Gertz and G. Marcy
Tue, 19 Apr 22
32/52

Comments: Accepted for publication in Journal of the British Interplanetary Society (JBIS)

Do anthropic arguments really work? [CEA]

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http://arxiv.org/abs/2204.07509


The anthropic explanation for the peculiarly small observed value of the cosmological constant $\Lambda_{\rm obs}$ argues that this value promotes the formation of stars, planets, and ultimately of observers such as ourselves. I show that a recent analytic model of cosmic star formation predicts that although $\Lambda_{\rm obs}$ maximises the overall efficiency of star formation in the universe, the probability of generating observers peaks at $\sim400-500 \, \Lambda_{\rm obs}$. These preliminary results suggest that an immediate connection between star formation efficiency and observers’ generation is not straightforward, and highlight the subtleties involved with the application of anthropic reasoning.

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D. Sorini
Mon, 18 Apr 22
15/34

Comments: contribution to the 2022 Cosmology session of the 56th Rencontres de Moriond

Avoiding the Great Filter: Predicting the Timeline for Humanity to Reach Kardashev Type I Civilization [CL]

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http://arxiv.org/abs/2204.07070


The level of technological development of any civilization can be gaged in large part by the amount of energy they produce for their use, but also encompasses that civilization’s stewardship of their home world. Following the Kardashev definition, a Type I civilization is able to store and use all the energy available on its planet. In this study, we develop a model based on Carl Sagan’s K formula and use this model to analyze the consumption and energy supply of the three most important energy sources: fossil fuels (e.g., coal, oil, natural gas, crude, NGL and feedstocks), nuclear energy and renewable energy. We also consider environmental limitations suggested by United Nations Framework Convention on Climate Change, the International Energy Agency, and those specific to our calculations to predict when humanity will reach the level of a Kardashev scale Type I civilization. Our findings suggest that the best estimate for this day will not come until year 2371.

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J. Jiang, F. Feng, P. Rosen, et. al.
Fri, 15 Apr 22
49/50

Comments: 15 pages, 7 figures, submitted to journal galaxies, currently under peer-review

The Number of Possible CETIs within Our Galaxy and the Communication Probability among These CETIs [EPA]

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http://arxiv.org/abs/2204.05479


As the only known intelligent civilization, human beings are always curious about the existence of other communicating extraterrestrial intelligent civilizations (CETIs). Based on the latest astrophysical information, we carry out Monte Carlo simulations to estimate the number of possible CETIs within our Galaxy and the communication probability among them. Two poorly known parameters have a great impact on the results. One is the probability of life appearing on terrestrial planets and eventually evolving a into CETI ($f_c$), and the other determines at what stage of their host star’s evolution CETIs would be born ($F$). In order to ensure the completeness of the simulation, we consider a variety of combinations of $f_c$ and $F$. Our results indicate that for optimistic situations (e.g. $F=25\%$ and $f_c=0.1\%$), there could be $42777_{-369}^{+267}$ CETIs and they need to survive for $3_{-2}^{+17}$ yr ($2000_{-1400}^{+2000}$ yr) to achieve one-way communication (two-way communication). In this case, human beings need to survive $0.3_{-0.298}^{+0.6}$ Myr to receive one alien signal. For pessimistic situations (e.g. $F=75\%$ and $f_c=0.001\%$), only $111_{-17}^{+28}$ CETIs could be born and they need to survive for $0.8_{-0.796}^{+1.2}$ Myr ($0.9_{-0.88}^{+4.1}$ Myr) to achieve one-way communication (two-way communication). In this case, human beings need to survive $50_{-49.6}^{+250}$ Myr to receive one signal from other CETIs. Our results may quantitatively explain why we have not detected any alien signals so far. The uncertainty of the results has been discussed in detail and would be alleviated with the further improvement of our astronomical observation ability in the future.

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W. Song and H. Gao
Wed, 13 Apr 22
13/73

Comments: Published in ApJ

Disruption of a Planetary Nitrogen Cycle as Evidence of Extraterrestrial Agriculture [EPA]

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http://arxiv.org/abs/2204.05360


Agriculture is one of the oldest forms of technology on Earth. The cultivation of plants requires a terrestrial planet with active hydrological and carbon cycles and depends on the availability of nitrogen in soil. The technological innovation of agriculture is the active management of this nitrogen cycle by applying fertilizer to soil, at first through the production of manure excesses but later by the Haber-Bosch industrial process. The use of such fertilizers has increased the atmospheric abundance of nitrogen-containing species such as NH$_3$ and N$_2$O as agricultural productivity intensifies in many parts of the world. Both NH$_3$ and N$_2$O are effective greenhouse gases, and the combined presence of these gases in the atmosphere of a habitable planet could serve as a remotely detectable spectral signature of technology. Here we use a synthetic spectral generator to assess the detectability of NH$_3$ and N$_2$O that would arise from present-day and future global-scale agriculture. We show that present-day Earth abundances of NH$_3$ and N$_2$O would be difficult to detect but hypothetical scenarios involving a planet with 30-100 billion people could show a change in transmittance of about 50-70% compared to pre-agricultural Earth. These calculations suggest the possibility of considering the simultaneous detection of NH$_3$ and N$_2$O in an atmosphere that also contains H$_2$O, O$_2$, and CO$_2$ as a technosignature for extraterrestrial agriculture. The technology of agriculture is one that could be sustainable across geologic timescales, so the spectral signature of such an “ExoFarm” is worth considering in the search for technosignatures.

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J. Haqq-Misra, T. Fauchez, E. Schwieterman, et. al.
Wed, 13 Apr 22
28/73

Comments: Accepted by ApJL, 12 pages, 1 figure

Finding the ET Signal from the Cosmic Noise [CL]

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http://arxiv.org/abs/2204.04405


This paper highlights a methodological approach designed to enhance the search for extraterrestrial intelligence (SETI) by hypothesizing that a transmission technosignature would likely have two features: 1) be wideband in the microwave or higher frequency range that originates from a hub within a supposed ET interplanetary navigation/communication (nav/comm) network, and 2) contain x-ray pulsar-based navigation (XNAV) metadata.
Potential contributions to the field include improved accuracy in finding transmission technosignatures and other technosignatures in the electromagnetic spectrum, a common standard in reaching a Schelling Point (a mutual realization of how we and ETs can find each other), and operationalizing models such as the Drake Equation.

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R. Davis
Tue, 12 Apr 22
8/87

Comments: 13 pages

COWS all tHE way Down (COWSHED) I: Could cow based planetoids support methane atmospheres? [EPA]

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http://arxiv.org/abs/2203.16609


More often than not a lunch time conversation will veer off into bizarre and uncharted territories. In rare instances these frontiers of conversation can lead to deep insights about the Universe we inhabit. This paper details the fruits of one such conversation. In this paper we will answer the question: How many cows do you need to form a planetoid entirely comprised of cows, which will support a methane atmoosphere produced by the planetary herd? We will not only present the necessary assumptions and theory underpinning the cow-culations, but also present a thorough (and rather robust) discussion of the viability of, and implications for accomplishing, such a feat.

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W. Roper, T. Cook, V. Korbina, et. al.
Fri, 1 Apr 22
6/85

Comments: N/A

Transmogrifiers: Bright of the Exomoon [CL]

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http://arxiv.org/abs/2203.17017


Though it may be a behavior that has been observed and documented for millennia, and despite the connection between it and the full moon, the astronomical community has afforded very little attention to lycanthropy. We hope to address this deficiency by using the population of known exoplanets as a natural experiment to better characterize what properties of the moon are necessary to trigger a transformation into a werewolf. We additionally investigate which exoplanets are most likely to have exomoons which may cause werewolves, with a particular focus on LHS 1140 b. We also propose a new mission called the Werewolves From Infrared Radiation and Spectral-typing Telescope, or WFIRST, in order to better characterize exoplanetary systems. This will allow us to explore the impact of stellar type on lycanthropy more than it has traditionally been considered. We believe this represents a major step forward in our understanding and recognition of the burgeoning field of exocryptozoology.

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M. Lund
Fri, 1 Apr 22
26/85

Comments: 11 pages, 2 figures. Submitted to Acta Prima Aprilia

The Three Little Pigs and the Big Bad Wolf: Case Studies of Peer Review [HEAP]

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http://arxiv.org/abs/2203.17095


I present for your appraisal three independent cases of the manuscript referee process conducted by a venerable peer-reviewed scientific journal. Each case involves a little pig, who submitted for consideration a theoretical plan for a house to be constructed presently, in a faraway land. An anonymous big bad wolf was assigned by the journal to assess the merit of these manuscripts. The pigs proposed three distinct construction frameworks, which varied in physical and mathematical sophistication. The first little pig submitted a model of straw, based on the numerical method of toe-counting. His design included odd features, such as spilled millet and cloven-hoofprints on the window sill — possibly a ploy to distract the wolf from the manuscript’s facile mathematical foundation. The second little pig used a more advanced approach, employing Newton’s classical laws of motion, to propose a house of sticks. This pig included in her manuscript copious citations by a specific wolf, possibly aiming to ensure acceptance by flattering the wolf whom she anticipated would be the referee. The third little pig described an ostentatious house of bricks based on an elaborate dynamical systems and stability analysis, possibly scheming to dazzle and impress. The big bad wolf did not appear moved by any of the pigs’ tactics. His recommendations were, for straw: the minor revision of water-proofing; for sticks: the major revision of fire-proofing, given concerns surrounding climate change; for bricks: unequivocal rejection, accompanied by multiple derogatory comments regarding “high-and-mighty theorists.” I describe each case in detail, and suggest that the wolf’s reports might be driven as much by self interest as the manuscripts themselves — namely, that at the time the wolf wrote the reviews, he was rather hungry. Finally, I examine morals learned, if any.

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E. Armstrong
Fri, 1 Apr 22
54/85

Comments: 7 pages, 6 figures. this http URL

Predicting Winners of the Reality TV Dating Show $\textit{The Bachelor}$ Using Machine Learning Algorithms [CL]

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http://arxiv.org/abs/2203.16648


$\textit{The Bachelor}$ is a reality TV dating show in which a single bachelor selects his wife from a pool of approximately 30 female contestants over eight weeks of filming (American Broadcasting Company 2002). We collected the following data on all 422 contestants that participated in seasons 11 through 25: their Age, Hometown, Career, Race, Week they got their first 1-on-1 date, whether they got the first impression rose, and what “place” they ended up getting. We then trained three machine learning models to predict the ideal characteristics of a successful contestant on $\textit{The Bachelor}$. The three algorithms that we tested were: random forest classification, neural networks, and linear regression. We found consistency across all three models, although the neural network performed the best overall. Our models found that a woman has the highest probability of progressing far on $\textit{The Bachelor}$ if she is: 26 years old, white, from the Northwest, works as an dancer, received a 1-on-1 in week 6, and did not receive the First Impression Rose. Our methodology is broadly applicable to all romantic reality television, and our results will inform future $\textit{The Bachelor}$ production and contestant strategies. While our models were relatively successful, we still encountered high misclassification rates. This may be because: (1) Our training dataset had fewer than 400 points or (2) Our models were too simple to parameterize the complex romantic connections contestants forge over the course of a season.

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A. Lee, G. Chesmore, K. Rocha, et. al.
Fri, 1 Apr 22
60/85

Comments: 6 Pages, 5 Figures. Submitted to Acta Prima Aprila. Code used in this work available at this http URL

The Parking Lot Planet [CL]

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http://arxiv.org/abs/2203.16791


We give conditions for an exoplanetary system to function as an ideal amusement park/vacation resort (with its separate parking lot, of course); in case of massive human interplanetary colonization. Our considerations stem from the fact that an amusement park needs a parking lot of roughly the same surface area, thus the best option for its construction would be a system with at least 2 planets close to each other for easy tourist transportation. We also discuss the likelihood of finding such a system out there to cut down on construction costs.

Read this paper on arXiv…

S. Best, F. Correa and J. Espinoza
Fri, 1 Apr 22
85/85

Comments: 4 pages, 4 figures, submitted to Acta Prima Aprilia

The Case for Technosignatures: Why They May Be Abundant, Long-lived, Highly Detectable, and Unambiguous [EPA]

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http://arxiv.org/abs/2203.10899


The intuition suggested by the Drake equation implies that technology should be less prevalent than biology in the galaxy. However, it has been appreciated for decades in the SETI community that technosignatures could be more abundant, longer-lived, more detectable, and less ambiguous than biosignatures. We collect the arguments for and against technosignatures’ ubiquity and discuss the implications of some properties of technological life that fundamentally differ from nontechnological life in the context of modern astrobiology: It can spread among the stars to many sites, it can be more easily detected at large distances, and it can produce signs that are unambiguously technological. As an illustration in terms of the Drake equation, we consider two Drake-like equations, for technosignatures (calculating N(tech)) and biosignatures (calculating N(bio)). We argue that Earth and humanity may be poor guides to the longevity term L and that its maximum value could be very large, in that technology can outlive its creators and even its host star. We conclude that while the Drake equation implies that N(bio)>>N(tech), it is also plausible that N(tech)>>N(bio). As a consequence, as we seek possible indicators of extraterrestrial life, for instance, via characterization of the atmospheres of habitable exoplanets, we should search for both biosignatures and technosignatures. This exercise also illustrates ways in which biosignature and technosignature searches can complement and supplement each other and how methods of technosignature search, including old ideas from SETI, can inform the search for biosignatures and life generally.

Read this paper on arXiv…

J. Wright, J. Haqq-Misra, A. Frank, et. al.
Tue, 22 Mar 22
36/82

Comments: Published in ApJ Letters

Opportunities for Technosignature Science in the Astro2020 Report [IMA]

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http://arxiv.org/abs/2203.08968


The Astro2020 report outlines numerous recommendations that could significantly advance technosignature science. Technosignatures refer to any observable manifestations of extraterrestrial technology, and the search for technosignatures is part of the continuum of the astrobiological search for biosignatures. The search for technosignatures is directly relevant to the “World and Suns in Context” theme and “Pathways to Habitable Worlds” program in the Astro2020 report. The relevance of technosignatures was explicitly mentioned in “E1 Report of the Panel on Exoplanets, Astrobiology, and the Solar System,” which stated that “life’s global impacts on a planet’s atmosphere, surface, and temporal behavior may therefore manifest as potentially detectable exoplanet biosignatures, or technosignatures” and that potential technosignatures, much like biosignatures, must be carefully analyzed to mitigate false positives. The connection of technosignatures to this high-level theme and program can be emphasized, as the report makes clear the purpose is to address the question “Are we alone?” This question is also presented in the Explore Science 2020-2024 plan as a driver of NASA’s mission.
This white paper summarizes the potential technosignature opportunities within the recommendations of the Astro2020 report, should they be implemented by funding agencies. The objective of this paper is to demonstrate the relevance of technosignature science to a wide range of missions and urge the scientific community to include the search for technosignatures as part of the stated science justifications for the large and medium programs that include the Infrared/Optical/Ultraviolet space telescope, Extremely Large Telescopes, probe-class far-infrared and X-ray missions, and various facilities in radio astronomy.

Read this paper on arXiv…

J. Haqq-Misra, S. Sheikh, M. Lingam, et. al.
Fri, 18 Mar 22
25/66

Comments: Unsolicited white paper by the NExSS Working Group on Technosignatures, 11 pages

Modern Cosmology, an Amuse-Gueule [CL]

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http://arxiv.org/abs/2203.04757


This essay is a nontechnical primer for a broader audience, in which I paint a broad-brush picture of modern cosmology. I begin by reviewing the evidence for the big bang, including the expansion of our Universe, the cosmic microwave background, and the primordial abundances of the light elements. Next, I discuss how these and other cosmological observations can be well explained by means of the concordance model of cosmology, putting a particular emphasis on the composition of the cosmic energy budget in terms of visible matter, dark matter, and dark energy. This sets the stage for a short overview of the history of the Universe from the earliest moments of its existence all the way to the accelerated expansion at late times and beyond. Finally, I summarize the current status of the field, including the challenges it is currently facing such as the Hubble tension, and conclude with an outlook onto the bright future that awaits us in the coming years and decades. The text is complemented by an extensive bibliography serving as a guide for readers who wish to delve deeper.

Read this paper on arXiv…

K. Schmitz
Thu, 10 Mar 22
6/60

Comments: 33 pages, 5 figures. Contribution to an upcoming book on cosmology that is going be published by Springer later this year. Comments welcome

A Beacon in the Galaxy: Updated Arecibo Message for Potential FAST and SETI Projects [CL]

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http://arxiv.org/abs/2203.04288


An updated, binary-coded message has been developed for transmission to extraterrestrial intelligences in the Milky Way galaxy. The proposed message includes basic mathematical and physical concepts to establish a universal means of communication followed by information on the biochemical composition of life on Earth, the Solar System’s time-stamped position in the Milky Way relative to known globular clusters, as well as digitized depictions of the Solar System, and Earth’s surface. The message concludes with digitized images of the human form, along with an invitation for any receiving intelligences to respond. Calculation of the optimal timing during a given calendar year is specified for potential future transmission from both the Five-hundred-meter Aperture Spherical radio Telescope in China and the SETI Institute’s Allen Telescope Array in northern California to a selected region of the Milky Way which has been proposed as the most likely for life to have developed. These powerful new beacons, the successors to the Arecibo radio telescope which transmitted the 1974 message upon which this expanded communication is in part based, can carry forward Arecibo’s legacy into the 21st century with this equally well-constructed communication from Earth’s technological civilization.

Read this paper on arXiv…

J. Jiang, H. Li, M. Chong, et. al.
Thu, 10 Mar 22
19/60

Comments: 27 Pages, 20 Figures, Submitted to the Journal of Galaxies

Detectability of Chlorofluorocarbons in the Atmospheres of Habitable M-dwarf Planets [EPA]

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http://arxiv.org/abs/2202.05858


The presence of chlorofluorocarbons (CFCs) in Earth’s atmosphere is a direct result of technology. Ozone-depleting CFCs have been banned by most countries, but some CFCs have persistent in elevated concentrations due to their long stratospheric lifetimes. CFCs are effective greenhouse gases and could serve as a remotely detectable spectral signature of technology. Here we use a three-dimensional climate model and a synthetic spectrum generator to assess the detectability of CFC-11 and CFC-12 as a technosignature on exoplanets. We consider the case of TRAPPIST-1e as well as a habitable Earth-like planet around a 3300 K M-dwarf star, with CFC abundances ranging from one to five times present-day levels. Assuming an optimistic James Webb Space Telescope (JWST) Mid Infrared Instrument (MIRI) low resolution spectrometer (LRS) noise floor level of 10 ppm to multiple co-added observations, we find that spectral features potentially attributable to present or historic Earth-level CFC features could be detected with a SNR $\ge 3-5$ on TRAPPIST-1e, if present, in $\sim 100$ hours of in-transit time. However, applying a very conservative 50 ppm noise floor to co-added observations, even a 5x Earth-level CFC would not be detectable no matter the observation time. Such observations could be carried out simultaneously and at no additional cost with searches for biosignature gases. Non-detection would place upper limits on the CFC concentration. We find that with the launch of JWST, humanity may be approaching the cusp of being able to detect passive atmospheric technosignatures equal in strength to its own around the nearest stars.

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J. Haqq-Misra, R. Kopparapu, T. Fauchez, et. al.
Tue, 15 Feb 22
65/75

Comments: Accepted by the Planetary Science Journal, 13 pages, 5 figures

Gaia as Solaris: An Alternative Default Evolutionary Trajectory [CL]

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http://arxiv.org/abs/2201.04956


Now that we know that Earth-like planets are ubiquitous in the universe, as well as that most of them are much older than the Earth, it is justified to ask to what extent evolutionary outcomes on other such planets are similar, or indeed commensurable, to the outcomes we perceive around us. In order to assess the degree of specialty or mediocrity of our trajectory of biospheric evolution, we need to take into account recent advances in theoretical astrobiology, in particular (i) establishing the history of habitable planets’ formation in the Galaxy, and (ii) understanding the crucial importance of “Gaian” feedback loops and temporal windows for the interaction of early life with its physical environment. Hereby we consider an alternative macroevolutionary pathway that may result in tight functional integration of all sub-planetary ecosystems, eventually giving rise to a true superorganism at the biospheric level. The blueprint for a possible outcome of this scenario has been masterfully provided by the great Polish novelist Stanis{\l}aw Lem in his 1961 novel Solaris. In fact, Solaris offers such a persuasive and powerful case for an “extremely strong” Gaia hypothesis that it is, arguably, high time to investigate it in a discursive astrobiological and philosophical context. In addition to novel predictions in the domain of potentially detectable biosignatures, some additional cognitive and heuristic benefits of studying such extreme cases of functional integration are briefly discussed.

Read this paper on arXiv…

S. Janković, A. Katić and M. Ćirković
Mon, 17 Jan 22
36/59

Comments: 20 pages, 1 figure; accepted in “Origins of Life and Evolution of Biospheres”

Gaia as Solaris: An Alternative Default Evolutionary Trajectory [CL]

Posted on by

http://arxiv.org/abs/2201.04956


Now that we know that Earth-like planets are ubiquitous in the universe, as well as that most of them are much older than the Earth, it is justified to ask to what extent evolutionary outcomes on other such planets are similar, or indeed commensurable, to the outcomes we perceive around us. In order to assess the degree of specialty or mediocrity of our trajectory of biospheric evolution, we need to take into account recent advances in theoretical astrobiology, in particular (i) establishing the history of habitable planets’ formation in the Galaxy, and (ii) understanding the crucial importance of “Gaian” feedback loops and temporal windows for the interaction of early life with its physical environment. Hereby we consider an alternative macroevolutionary pathway that may result in tight functional integration of all sub-planetary ecosystems, eventually giving rise to a true superorganism at the biospheric level. The blueprint for a possible outcome of this scenario has been masterfully provided by the great Polish novelist Stanis{\l}aw Lem in his 1961 novel Solaris. In fact, Solaris offers such a persuasive and powerful case for an “extremely strong” Gaia hypothesis that it is, arguably, high time to investigate it in a discursive astrobiological and philosophical context. In addition to novel predictions in the domain of potentially detectable biosignatures, some additional cognitive and heuristic benefits of studying such extreme cases of functional integration are briefly discussed.

Read this paper on arXiv…

S. Janković, A. Katić and M. Ćirković
Mon, 17 Jan 22
23/59

Comments: 20 pages, 1 figure; accepted in “Origins of Life and Evolution of Biospheres”

Symmetries in Stellar, Galactic and Extragalactic Astronomy [CL]

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http://arxiv.org/abs/2201.04966


Examples are presented for appearance of geometric symmetry in the shape of various astronomical objects and phenomena. Usage of these symmetries in astrophysical and extragalactic research is also discussed.

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L. Szabados
Fri, 14 Jan 22
41/52

Comments: 13 pages, 10 figures. Appeared as a chapter in the book Complex Symmetries (ed. G. Darvas), Birkh\”auser (2022), pp.191-205. ISBN 978-3-030-88058-3. The content in this version is identical with that of the published paper, but the layout is somewhat different

Radio bridges of the future between Solar system and the nearest 50 stars [CL]

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http://arxiv.org/abs/2201.04969


The Solar Gravitational Lens (SGL) is a gift of nature that Humanity is now ready to exploit. SGL physics started with Einstein’s 1936 paper on the gravitational lensing; it was not until 1979 that the idea of a space mission reaching the Sun’s nearest focal sphere at 550 Astronomical Units (AU) was put forward by Von Eshleman. By the year 2000, the senior author of this paper (CM) had submitted a relevant formal proposal to ESA about the relevant space mission to 550 AU. He presented his ideas at NASA-JPL for the first time on August 18. In 2020 NASA awarded a $2million grant to JPL to prepare for the first FOCAL space mission. But radio bridges between the Sun and any nearby star may also be conceived. The idea is that, if Humanity will be able to send unmanned space probes to the nearest stars in the future, each of these probes could be placed behind the star of arrival and along the star-Sun line, thus allowing for TWO gravitational lenses to work together. That will result in a permanent communication system with much REDUCED POWERS to keep the radio link between the two stellar systems: a veritable Galactic Internet. In this paper, we study for the first time the 50 radio bridges between the Sun and each of the nearest 100 stars in the Galaxy. Of course, this work is for the centuries to come. But knowing which natural radio bridge between the Sun and each of the nearest 50 stars is MORE CONVENIENT, will open the ROAD MAP for the HUMAN EXPANSION into the Galaxy.

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C. Maccone and N. Antonietti
Fri, 14 Jan 22
42/52

Comments: N/A

Gravity-Assist as a Solution to Save Earth from Global Warming [EPA]

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http://arxiv.org/abs/2201.02879


Global warming is one of the problems of human civilization and decarbonization policy is the main solution to this problem. In this work, we propose using the gravity-assist by the asteroids to increase the orbital distance of the Earth from the Sun. We can manipulate the orbit of asteroids in the asteroid belt by solar sailing and propulsion engines to guide them towards the Mars orbit and a gravitational scattering can put asteroids in a favorable direction to provide an energy loss scattering from the Earth. The result would be increasing the orbital distance of the earth and consequently cooling down the Earth’s temperature. We calculate the increase in the orbital distance of the earth for each scattering and investigate the feasibility of performing this project.

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S. Rahvar
Tue, 11 Jan 22
92/95

Comments: 4 pages, 2 figures

Illuminating the Darkest Galaxies [CEA]

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http://arxiv.org/abs/2112.04657


Low luminosity dwarf galaxies provide stringent constraints on the nature of dark matter. Establishing these constraints depends on precise kinematic measurements of individual stars. In this overview for non-specialists, we describe current and future prospects for three unique tests of dark matter using resolved stellar kinematics in low luminosity galaxies: the overall number of satellite galaxies around the Milky Way, dark-matter annihilation radiation from dwarf galaxies, and their internal density profiles. We then assess the prospects for meaningfully testing theories of dark matter based on the improved kinematic precision expected from upcoming facilities.

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J. Simon and M. Geha
Fri, 10 Dec 21
54/94

Comments: This review article appeared in Physics Today, November 2021, see this http URL

A radio technosignature search towards Proxima Centauri resulting in a signal-of-interest [IMA]

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http://arxiv.org/abs/2111.08007


The detection of life beyond Earth is an ongoing scientific endeavour, with profound implications. One approach, known as the search for extraterrestrial intelligence (SETI), seeks to find engineered signals (technosignatures') that indicate the existence technologically-capable life beyond Earth. Here, we report on the detection of a narrowband signal-of-interest at ~982 MHz, recorded during observations toward Proxima Centauri with the Parkes Murriyang radio telescope. This signal,BLC1′, has characteristics broadly consistent with hypothesized technosignatures and is one of the most compelling candidates to date. Analysis of BLC1 — which we ultimately attribute to being an unusual but locally-generated form of interference — is provided in a companion paper (Sheikh et al., 2021). Nevertheless, our observations of Proxima Centauri are the most sensitive search for radio technosignatures ever undertaken on a star target.

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S. Smith, D. Price, S. Sheikh, et. al.
Wed, 17 Nov 21
2/64

Comments: 14 pages, 4 figures (+3 supplementary figures). Published open-access in Nature Astronomy

How to create an artificial magnetosphere for Mars [CL]

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http://arxiv.org/abs/2111.06887


If humanity is ever to consider substantial, long-term colonization of Mars, the resources needed are going to be extensive. For a long-term human presence on Mars to be established, serious thought would need to be given to terraforming the planet. One major requirement for such terraforming is having the protection of a planetary magnetic field which Mars currently does not have. In this article we explore comprehensively for the first time, the practical and engineering challenges that affect the feasibility of creating an artificial magnetic field capable of encompassing Mars. This includes the concerns that define the design, where to locate the magnetic field generator and possible construction strategies. The rationale here is not to justify the need for a planetary magnetosphere but to put figures on the practicalities so as to be able to weigh the pros and cons of the different engineering approaches.
The optimum solution proposed is completely novel, although inspired by natural situations and fusion plasma techniques. The solution with the lowest power, assembly and mass is to create an artificial charged particle ring (similar in form to a “radiation belt”), around the planet possibly formed by ejecting matter from one of the moons of Mars (in fashion similar to that that forms the Io-Jupiter plasma torus), but using electromagnetic and plasma waves to drive a net current in the ring(s) that results in an overall magnetic field.
With a new era of space exploration underway, this is the time to start thinking about these new and bold future concepts and to begin filling strategic knowledge gaps. Furthermore, the principles explored here are also applicable to smaller scale objects like manned spacecraft, space stations or moon bases, which would benefit from the creation of protective mini-magnetospheres.

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R. Bamford, B. Kellett, J. Green, et. al.
Tue, 16 Nov 21
15/97

Comments: Accepted for publication Acta Astronautica Sept 2021

Research Programs Arising from 'Oumuamua Considered as an Alien Craft [EPA]

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http://arxiv.org/abs/2111.07895


The controversial hypothesis that ‘Oumuamua (1I/2017 U1) was an alien craft dominated by a solar sail is considered using known physics for the two possible cases: controlled and uncontrolled flight. The reliability engineering challenges for an artifact designed to operate for 10^5 – 10^6 yr are also considerable. All three areas generate research programs going forward. The uncontrolled case could be either “anonymous METI” (messaging extraterrestrial intelligence) or “inadvertent METI”. In the controlled case the nature of the origin star, trajectory guidance from the origin star to the Sun, and the identity of a destination star are all undecided. The “controlled” case has more strikes against it than the “uncontrolled” case, but neither suffers a knock-out blow, as yet. Some of the issues turn out not to be major obstacles to the alien craft hypothesis, but others weaken the case for it. Most, however, imply new studies. Some of these, e.g., intercept missions for new interstellar objects, are concepts being developed, and will be of value whatever these objects turn out to be. Overall, these considerations show that a many pronged, targeted, research program can be built around the hypothesis that’Oumuamua is an alien craft. The considerations presented here can also be applied to other interstellar visitors, as well as to general discussions of interstellar travel.

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M. Elvis
Tue, 16 Nov 21
40/97

Comments: 17 pages, 1 figure, 1 table. International Journal of Astrobiology, in press

Analysis of the Breakthrough Listen signal of interest blc1 with a technosignature verification framework [IMA]

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http://arxiv.org/abs/2111.06350


The aim of the search for extraterrestrial intelligence (SETI) is to find technologically-capable life beyond Earth through their technosignatures. On 2019 April 29, the Breakthrough Listen SETI project observed Proxima Centauri with the Parkes ‘Murriyang’ radio telescope. These data contained a narrowband signal with characteristics broadly consistent with a technosignature near 982 MHz (‘blc1’). Here we present a procedure for the analysis of potential technosignatures, in the context of the ubiquity of human-generated radio interference, which we apply to blc1. Using this procedure, we find that blc1 is not an extraterrestrial technosignature, but rather an electronically-drifting intermodulation product of local, time-varying interferers aligned with the observing cadence. We find dozens of instances of radio interference with similar morphologies to blc1 at frequencies harmonically related to common clock oscillators. These complex intermodulation products highlight the necessity for detailed follow-up of any signal-of-interest using a procedure such as the one outlined in this work.

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S. Sheikh, S. Smith, D. Price, et. al.
Fri, 12 Nov 21
32/53

Comments: 15 pages of main paper followed by 19 pages of supplementary material; 22 figures total; published open-access in Nature Astronomy

The First Interstellar Astronauts Will Not Be Human [EPA]

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http://arxiv.org/abs/2110.13080


Our ability to explore the cosmos by direct contact has been limited to a small number of lunar and interplanetary missions. However, the NASA Starlight program points a path forward to send small, relativistic spacecraft far outside our solar system via standoff directed-energy propulsion. These miniaturized spacecraft are capable of robotic exploration but can also transport seeds and organisms, marking a profound change in our ability to both characterize and expand the reach of known life. Here we explore the biological and technological challenges of interstellar space biology, focusing on radiation-tolerant microorganisms capable of cryptobiosis. Additionally, we discuss planetary protection concerns and other ethical considerations of sending life to the stars.

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S. Lantin, S. Mendell, G. Akkad, et. al.
Tue, 26 Oct 21
5/109

Comments: 17 pages, 3 figures

The Search for Deliberate Interstellar SETI Signals May Be Futile [CL]

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http://arxiv.org/abs/2110.11502


For more than 60 years, the predominant SETI search paradigm has entailed the observation of stars in an effort to detect alien electromagnetic signals that deliberately target Earth. However, this strategy is fraught with challenges when examined from ETs perspective. Astronomical, physiological, psychological, and intellectual problems are enumerated. Consequently, ET is likely to attempt a different strategy in order to best establish communications. It will send physical AI robotic probes that would be linked together by a vast interstellar network of communications nodes. This strategy would solve most or all problems associated with interstellar signaling.

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J. Gertz
Mon, 25 Oct 21
9/76

Comments: Accepted for publication in JBIS

Feasibility Study For Hydrogen Producing Colony on Mars [CL]

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http://arxiv.org/abs/2110.10795


A technologically mature colony on Mars can produce and deliver at least 1 million tons of liquid hydrogen per year to one or more propellant depots at Low Earth Orbit (LEO). Production of 1 $kg$ of hydrogen at Marian colony and its delivery to LEO requires an energy expenditure of 1.4 $GJ$ on Mars. LEO propellant depot contains hydrogen produced on Mars and oxygen produced on the Moon or near-Earth asteroids. This propellant is used to deliver payload from LEO to many destinations in the Solar System including Mars. Delivery of 1 $kg$ payload from LEO to Mars requires an energy expenditure of 3.5 $GJ$ on Mars, Moon, and near-Earth asteroids. The use of liquid hydrogen produced on Mars to deliver astronauts and payload to Mars ensures exponential bootstrap growth of the Martian colony. Martian Colony and delivery of millions of tons of liquid hydrogen to LEO is the key to Colonization of Solar System. %% Martian Colony starts transporting liquid hydrogen to LEO only after it grows to significant size. It should contain about 20 million tons of steel and 3 million tons of plastic in structures and material as well as several thousand astronauts. Prior to that time, LEO hydrogen deposit will be supplied by hydrogen from Lunar poles.

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D. Shubov
Fri, 22 Oct 21
6/133

Comments: N/A

Nebula-Relay Hypothesis: The Chirality of Biological Molecules in Molecular Clouds [CL]

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http://arxiv.org/abs/2110.02524


The origin of chirality in the molecules of life is thought to be closely related to the origin of life and still an unsolved mystery for a long time. Previously, we proposed a new model of the origin of life, named Nebula-Relay Nebula-Relay, which assumed that the life on Earth originated at the planetary system of sun’s predecessor star and then filled in the pre-solar nebula after the its death. As primitive lives existed in the molecular cloud until the formation of solar system, does the chirality of biomolecules occured during this period? We explore such possibility in this work and find that the ultra-low temperature environment is very beneficial to generate the chiral polymer chain of biological molecules.

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L. Feng
Thu, 7 Oct 21
6/51

Comments: 8 pages, 2 figures

Can the China's FAST telescope detect extraterrestrial von-Neumann probes? [CL]

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http://arxiv.org/abs/2110.00406


In the present paper we consider the Type-2.x and Type-3.x extraterrestrial von-Neumann probes and study the problem of their detectability by the world’s largest radio telescope: the Five-hundred-meter Aperture Spherical Radio Telescope (FAST). For this purpose we estimate the radio spectral parameters and analyse the obtained results in the context of technical characteristics of FAST. As a result, it is shown that FAST can detect as galactic as well as extragalactic self-replicating probes with high precision.

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Z. Osmanov
Mon, 4 Oct 21
39/76

Comments: 6 pages, 0 figures

Teaching relativity at the AstroCamp [CL]

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http://arxiv.org/abs/2109.13270


The AstroCamp is an academic excellence program in the field of astronomy and physics for students in the last 3 years of pre-university education, which often includes a course (or a significant part thereof) on Relativity. After an introduction to the principles, goals and structure of the camp, I describe the approach followed by camp lecturers (myself and others) for teaching Special and General Relativity, and some lessons learned and feedback from the students. I also provide some thoughts on the differences between the physics and mathematics secondary school curricula in Portugal and in other countries, and on how these curricula could be modernized.

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C. Martins
Wed, 29 Sep 21
11/78

Comments: Summary of a talk given at the Teaching Einsteinian Physics to School Students parallel session of the Sixteenth Marcel Grossmann Meeting. To appear in the proceedings

Stellar Gravitational Lens Engineering for Interstellar Communication and Artifact SETI [IMA]

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http://arxiv.org/abs/2109.08657


Several recent works have proposed “stellar relay” transmission systems in which a spacecraft at the focus of a star’s gravitational lens achieves dramatic boosts in the gain of an outgoing or incoming interstellar transmission. We examine some of the engineering requirements of a stellar relay system, evaluate the long-term sustainability of a gravitational relay, and describe the perturbations and drifts that must be actively countered to maintain a relay-star-target alignment. The major perturbations on a relay-Sun-target alignment are the inwards gravity of the Sun and the reflex motion of the Sun imparted by the planets. These approx. m/s/yr accelerations can be countered with modern propulsion systems over century-long timescales. This examination is also relevant for telescope designs aiming to use the Sun as a focusing element. We additionally examine prospects for an artifact SETI search to observe stellar relays placed around the Sun by an extraterrestrial intelligence and suggest certain nearby stars that are relatively unperturbed by planetary systems as favorable nodes for a stellar relay communications system.

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S. Kerby and J. Wright
Mon, 20 Sep 21
25/53

Comments: 13 pages, 1 figure, 2 tables

The Dark Side of the Universe [CL]

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http://arxiv.org/abs/2108.01691


A view on the history and current status of dark matter and dark energy, at a fairly introductory level.

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A. Rújula
Thu, 5 Aug 21
9/57

Comments: 26 pages. 11 figures

Avoiding the "Great Filter": A Projected Timeframe for Human Expansion Off-World [CL]

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http://arxiv.org/abs/2108.01730


A foundational model has been developed based on trends built from empirical data of space exploration and computing power through the first six plus decades of the Space Age which projects earliest possible launch dates for human-crewed missions from cis-lunar space to selected Solar System and interstellar destinations. The model uses computational power, expressed as transistors per microprocessor, as a key broadly limiting factor for deep space missions’ reach and complexity. The goal of this analysis is to provide a projected timeframe for humanity to become a multi-world species through off-world colonization, and in so doing all but guarantees the long-term survival of the human race from natural and human-caused calamities that could befall life on Earth. Be-ginning with the development and deployment of the first nuclear weapons near the end of World War II, humanity entered a ‘Window of Peril’ which will not be safely closed until robust off-world colonies become a reality. Our findings suggest the first human-crewed missions to land on Mars, selected Asteroid Belt objects, and selected moons of Jupiter and Saturn can occur before the end of the 21st century. Launches of human-crewed interstellar missions to exoplanet destinations within roughly 40 lightyears of the Solar System are seen as possible during the 23rd century and launch of intragalactic missions by the end of the 24th century. An aggressive and sustained space exploration program, which includes colonization, is thus seen as critical to the long-term survival of the human race.

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J. Jiang, P. Rosen and K. Fahy
Thu, 5 Aug 21
20/57

Comments: N/A

Completing Aganta Kairos: Capturing Metaphysical Time on the Seventh Continent [CL]

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http://arxiv.org/abs/2108.01687


We present an overview of the art project Aganta Kairos (To Fish the Metaphysical Time). This project celebrates the neutrino, the ghost particle, which scientists consider a cosmic messenger and the artist regards as a link between people who care about their relationship to the cosmos and question their origins. The artwork is based on a performance of celebration and seeks to build a human community that encompasses different knowledge domains and interpretations of the universe. This intersection of knowledge is realized during the performance of placing a plaque, held with witnesses, and during subsequent exhibitions. Images, sounds, videos, and sculpture testify to the diversity of approaches to questioning our origins, ranging from traditional western science to ancient shamanism. The sites were selected for their global coverage and, for the South Pole, Mediterranean, and Lake Baikal, their connection to ongoing neutrino experiments. In December 2020, a plaque was installed at the South Pole IceCube Laboratory, the seventh and final site. We provide examples of images and links to additional images and videos.

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J. Madsen, L. Mulot and C. Spiering
Thu, 5 Aug 21
54/57

Comments: Presented at the 37th International Cosmic Ray Conference (ICRC 2021). See arXiv:2107.06966 for all IceCube contributions

Intelligent Responses to Our Technological Signals Will Not Arrive In Fewer Than Three Millennia [CL]

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http://arxiv.org/abs/2108.01690


What is the chance we start a conversation with another civilization like our own? Our technological society produced signals that could be received by other extraterrestrial civilizations, within a sphere around us with a radius of $\sim 10^2$ light years. Given that, the Copernican principle provides a lower limit on the response time that we should expect from transmitters on Earth-like planets around Sun-like stars. If our civilization lives longer, the expected number of responses could increase. We explore the chance of detecting a response in the future, and show that a response should only be expected to arrive after a few millennia.

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A. Siraj and A. Loeb
Thu, 5 Aug 21
56/57

Comments: 4 pages, 4 figures; submitted for publication

Limits of Detecting Extraterrestrial Civilizations [CL]

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http://arxiv.org/abs/2107.09794


The search for extraterrestrial intelligence (SETI) is a scientific endeavor which struggles with unique issues — a strong indeterminacy in what data to look for and when to do so. This has led to attempts at finding both fundamental limits of the communication between extraterrestrial intelligence and human civilizations, as well as benchmarks so as to predict what kinds of signals we might most expect. Previous work has been formulated in terms of the information-theoretic task of communication, but we instead argue it should be viewed as a detection problem, specifically one-shot (asymmetric) hypothesis testing. With this new interpretation, we develop fundamental limits as well as provide simple examples of how to use this framework to analyze and benchmark different possible signals from extraterrestrial civilizations. We show that electromagnetic signaling for detection requires much less power than for communication, that detection as a function of power can be non-linear, and that much of the analysis in this framework may be addressed using computationally efficient optimization problems, thereby demonstrating tools for further inquiry.

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I. George, X. Chen and L. Varshney
Thu, 22 Jul 21
3/59

Comments: Main Text: 16 pages, 1 Figure. Comments welcome

SETI in 2020 [IMA]

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http://arxiv.org/abs/2107.07512


In the spirit of Trimble’s “Astrophysics in XXXX” series, I very briefly and subjectively review developments in SETI in 2020. My primary focus is 74 papers and books published or made public in 2020, which I sort into six broad categories: results from actual searches, new search methods and instrumentation, target and frequency seleciton, the development of technosignatures, theory of ETIs, and social aspects of SETI.

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J. Wright
Mon, 19 Jul 21
69/70

Comments: Submitted to Acta Astronautica. Community input and suggestions solicited

Strategies and Advice for the Search for Extraterrestrial Intelligence [IMA]

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http://arxiv.org/abs/2107.07283


As a guide for astronomers new to the field of technosignature search (i.e. SETI), I present an overview of some of its observational and theoretical approaches. I review some of the various observational search strategies for SETI, focusing not on the variety of technosignatures that have been proposed or which are most likely to be found, but on the underlying philosophies that motivate searches for them. I cover passive versus active searches, ambiguous versus dispositive kinds of technosignatures, commensal or archival searches versus dedicated ones, communicative signals versus “artifacts”, “active” versus derelict technologies, searches for beacons versus eavesdropping, and model-based versus anomaly-based searches. I also attempt to roughly map the landscape of technosignatures by kind and the scale over which they appear. I also discuss the importance of setting upper limits in SETI, and offer a heuristic for how to do so in a generic SETI search. I mention and attempt to dispel several misconceptions about the field. I conclude with some personal observations and recommendations for how to practice SETI, including how to choose good theory projects, how to work with experts and skeptics to improve one’s search, and how to plan for success.

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J. Wright
Fri, 16 Jul 21
10/61

Comments: 20 pages, two figures. Accepted to Acta Astronautica

A Dyson Sphere around a black hole [HEAP]

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http://arxiv.org/abs/2106.15181


The search for extraterrestrial intelligence (SETI) has been conducted for nearly 60 years. A Dyson Sphere, a spherical structure that surrounds a star and transports its radiative energy outward as an energy source for an advanced civilisation, is one of the main targets of SETI. In this study, we discuss whether building a Dyson Sphere around a black hole is effective. We consider six energy sources: (i) the cosmic microwave background, (ii) the Hawking radiation, (iii) an accretion disk, (iv) Bondi accretion, (v) a corona, and (vi) relativistic jets. To develop future civilisations (for example, a Type II civilisation), $4\times10^{26}\,{\rm W}$($1\,{\rm L_{\odot}}$) is expected to be needed. Among (iii) to (vi), the largest luminosity can be collected from an accretion disk, reaching $10^{5}\,{\rm L_{\odot}}$, enough to maintain a Type II civilisation. Moreover, if a Dyson Sphere collects not only the electromagnetic radiation but also other types of energy (e.g., kinetic energy) from the jets, the total collected energy would be approximately 5 times larger. Considering the emission from a Dyson Sphere, our results show that the Dyson Sphere around a stellar-mass black hole in the Milky Way ($10\,\rm kpc$ away from us) is detectable in the ultraviolet$(\rm 10-400\,{\rm nm)}$, optical$(\rm 400-760\,{\rm nm)}$, near-infrared($\rm 760\,{\rm nm}-5\,{\rm \mu m}$), and mid-infrared($\rm 5-40\,{\rm \mu m}$) wavelengths via the waste heat radiation using current telescopes such as Galaxy Evolution Explorer Ultraviolet Sky Surveys. Performing model fitting to observed spectral energy distributions and measuring the variability of radial velocity may help us to identify these possible artificial structures.

Read this paper on arXiv…

T. Hsiao, T. Goto, T. Hashimoto, et. al.
Wed, 30 Jun 21
3/79

Comments: This paper have accepted for publication in MNRAS

Galactic Traversability: A New Concept for Extragalactic SETI [GA]

Posted on by

http://arxiv.org/abs/2106.07739


Interstellar travel in the Milky Way is commonly thought to be a long and dangerous enterprise, but are all galaxies so hazardous? I introduce the concept of galactic traversability to address this question. Stellar populations are one factor in traversability, with higher stellar densities and velocity dispersions aiding rapid spread across a galaxy. The interstellar medium (ISM) is another factor, as gas, dust grains, and cosmic rays (CRs) all pose hazards to starfarers. I review the current understanding of these components in different types of galaxies, and conclude that red quiescent galaxies without star formation have favorable traversability. Compact elliptical galaxies and globular clusters could be “super-traversable”, because stars are packed tightly together and there are minimal ISM hazards. Overall, if the ISM is the major hindrance to interstellar travel, galactic traversability increases with cosmic time as gas fractions and star formation decline. Traversability is a consideration in extragalactic surveys for the search for extraterrestrial intelligence (SETI).

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B. Lacki
Wed, 16 Jun 21
23/57

Comments: 19 pages (11 pages of text), 2 tables, submitted

The Detectability of Nightside City Lights on Exoplanets [EPA]

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http://arxiv.org/abs/2105.09990


I estimate the detectability of nightside city lights on habitable, Earth-like, exoplanets around nearby stars using direct-imaging observations from the proposed LUVOIR and HabEx observatory architectures. I used data from the Soumi National Polar-orbiting Partnership satellite to determine the broadband surface flux from city lights at the top of Earth’s atmosphere, and the spectra of commercially available high-power lamps to model the spectral energy distribution of the emitted flux from city lights. I also consider how the detectability scales with urbanization fraction: from Earth’s value of $0.05\%$, up to the limiting case of an ecumenopolis — or planet-wide city. I then calculate the minimum detectable urbanization fraction using 100 hours of observing time for generic Earth-analogs around stars with 10 pc of the Sun and for nearby known potentially habitable planets. Though Earth itself would not be detectable by LUVOIR or HabEx, planets around M-dwarfs close to the Sun would show detectable signals from city lights for urbanization levels of $0.4\%$ to $3\%$, while the city lights on planets around nearby Sun-like stars would be detectable at urbanization levels of $\gtrsim10\%$. The known planet Proxima b is a particularly compelling target for LUVOIR A observations, which would be able to detect city lights at an urbanization level ten times that of Earth in 100 hours, a level of urbanization that is expected to occur on Earth around the mid-22nd-century. An ecumenopolis, or planet-wide city, would be detectable around roughly 80 nearby stars by both LUVOIR and HabEx, and a survey of all these systems would be able to place a $1\sigma$ upper limit of $\lesssim1.4\%$ on the frequency of ecumenopolis planets in the Solar neighborhood assuming no detections.

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T. Beatty
Mon, 24 May 21
15/41

Comments: Submitted to MNRAS. Comments welcome

Will Betelguese Explode? [CL]

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http://arxiv.org/abs/2105.09791


Since October 2019, Betelgeuse began to dim noticeably and by January 2020 its brightness had dropped by a factor of approximately 2.5, demoting it from the position of the top (apparent) brightest 11 th star to the 21 st!!! Astronomers were excited and thought of it as the lull before the storm, Betelguese was ready to go supernova!!!
This article is aimed more as a case study where we show how this question was answered using scientific arguments and data. It will also highlight the importance of supernovae to human existence and give a brief discussion on the evolution of massive stars.
And also, answer the question!!!

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P. Hasan
Fri, 21 May 21
49/66

Comments: Accepted in Resonance

Detectability of Artificial Lights from Proxima b [EPA]

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http://arxiv.org/abs/2105.08081


We investigate the possibility of detecting artificial lights from Proxima b’s dark side by computing light curves from the planet and its host star. The two different scenarios we consider are artificial illumination with the same spectrum as commonly used LEDs on Earth, and a narrower spectrum which leads to the same proportion of light as the total artificial illumination on Earth. We find that the James Webb Space Telescope (JWST) will be able to detect LED type artificial lights making up 5% of stellar power with 85% confidence, assuming photon-limited precision. In order for JWST to detect the current level of artificial illumination on Earth, the spectral band must be 10^3 times narrower. Our predictions require optimal performance from the NIRSpec instrument, and even if not possible with JWST, future observatories like LUVOIR might be able to detect this artificial illumination.

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E. Tabor and A. Loeb
Wed, 19 May 21
14/64

Comments: 4 pages, 3 figures

Neutrinos as a probe of the Universe [CL]

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http://arxiv.org/abs/2105.07502


A brief essay on how studying neutrinos can help us to better understand the Universe.

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L. Anchordoqui and T. Weiler
Tue, 18 May 21
30/77

Comments: To be published in The Innovation Platform; this https URL

The Drake Equation at 60: Reconsidered and Abandoned [CL]

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http://arxiv.org/abs/2105.03984


Each of the individual factors of the Drake Equation is considered. Each in turn is either abandoned or redefined and finally reduced to a single new factor, fd, the fraction of technological life that is detectable by any means. However, neither the Drake Equation, nor its replacement, can actually solve for N. Only a vibrant SETI program and, ultimately, contact with an alien civilization might result in the determination of N.

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J. Gertz
Tue, 11 May 21
79/93

Comments: 27 pages, Accepted for publication to JBIS

Modified Newtonian Gravity: Explaining observations of sub- and super-Chandrasekhar limiting mass white dwarfs [CL]

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http://arxiv.org/abs/2105.01702


The idea of possible modification to gravity theory, whether it is in the Newtonian or general relativistic premises, is there for quite sometime. Based on it, astrophysical and cosmological problems are targeted to solve. But none of the Newtonian theories of modification has been performed from the first principle. Here, we modify Poisson’s equation and propose two possible ways to modify the law gravitation which, however, reduces to Newton’s law far away from the center of source. Based on these modified Newton’s laws, we attempt to solve problems lying with white dwarfs. There are observational evidences for possible violation of the Chandrasekhar mass-limit significantly: it could be sub- as well as super-Chandrasekhar. We show that modified Newton’s law, either by modifying LHS or RHS of Poisson’s equation, can explain them.

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A. Sharma and B. Mukhopadhyay
Fri, 7 May 21
58/61

Comments: 9 pages including 4 figures; published in Scientific Voyage (ISSN: 2395-5546); this http URL

Combined Airborne Wind and Photovoltaic Energy System for Martian Habitats [IMA]

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http://arxiv.org/abs/2104.09506


Generating renewable energy on Mars is technologically challenging. Firstly, because compared to Earth, key energy resources such as solar and wind are weak as a result of very low atmospheric pressure and low solar irradiation. Secondly, because of the harsh environmental conditions, the required high degree of automation and the exceptional effort and costs to transport material to the planet. Like on Earth, it is crucial to combine complementary resources for an effective renewable energy solution. In this work, we present the result of a design synthesis exercise, a 10 kW microgrid solution, based on a pumping kite power system and photovoltaic solar modules to power the construction as well as the subsequent use of a Mars habitat. To buffer unavoidable energy fluctuations and balance seasonal and diurnal resource variations, the two energy systems are combined with a compressed gas storage system and lithium-sulfur batteries. The airborne wind energy solution was selected because of its low weight-to-wing-surface-area ratio, compact packing volume and high capacity factor which enables it to endure strong dust storms in an airborne parking mode. The surface area of the membrane wing is 50 m2 and the mass of the entire system, including the kite control unit and ground station, is 290 kg. The performance of the microgrid is assessed by computational simulation using available resource data for a chosen deployment location on Mars. The projected costs of the system are 8.95 million Euro, excluding transportation to Mars.

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L. Ouroumova, D. Witte, B. Klootwijk, et. al.
Wed, 21 Apr 2021
11/72

Comments: N/A

The Draconic gearing of the Antikythera Mechanism Assembling the Fragment D on the Antikythera Mechanism: Its role and operation [CL]

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http://arxiv.org/abs/2104.06181


The unplaced Fragment D of the Antikythera Mechanism with unknown operation, was a mystery since the beginning of its discovery. The gear r1, which was detected on the Fragment radiographies by C. Karakalos, is preserved in very good condition, but this was not enough to correlate it to the existing gear trainings of the Mechanism. According to recent researches and observations, the planet gearing indication on the Antikythera Mechanism is not probable, so the operation and position of gear r1, was still unknown. Based on Fragment A gearing trains, an ideal operation and proper position of this enigmatic gear/part of the Mechanism, is presented, analyzed and discussed, taking into account all of the mechanical characteristics and the other two parts of the Fragment D, visible in AMRP tomographies. The described operation and position of Fragment D, gives answers on several questions and improves the Mechanism functionality, contributing to the completion of the Antikythera Mechanism puzzle.

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A. A.Voulgaris, C. C.Mouratidis, A. A.Vossinakis, et. al.
Wed, 14 Apr 2021
34/67

Comments: Submitted on January 14, 2020

Astro-animation – A Case Study of Art and Science Education [CL]

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http://arxiv.org/abs/2104.06215


Art and science are different ways of exploring the world, but together they have the potential to be thought-provoking, facilitate a science-society dialogue, raise public awareness of science, and develop an understanding of art. For several years, we have been teaching an astro-animation class at the Maryland Institute College of Art as a collaboration between students and NASA scientists. Working in small groups, the students create short animations based on the research of the scientists who are going to follow the projects as mentors. By creating these animations, students bring the power of their imagination to see the research of the scientists through a different lens. Astro-animation is an undergraduate-level course jointly taught by an astrophysicist and an animator. In this paper we present the motivation behind the class, describe the details of how it is carried out, and discuss the interactions between artists and scientists. We describe how such a program offers an effective way for art students, not only to learn about science but to have a glimpse of “science in action”. The students have the opportunity to become involved in the process of science as artists, as observers first and potentially through their own art research. Every year, one or more internships at NASA Goddard Space Flight Center have been available for our students in the summer. Two students describe their experiences undertaking these internships and how science affects their creation of animations for this program and in general. We also explain the genesis of our astro-animation program, how it is taught in our animation department, and we present the highlights of an investigation of the effectiveness of this program we carried out with the support of an NEA research grant. In conclusion we discuss how the program may grow in new directions, such as contributing to informal STE(A)M learning.

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L. Arcadias, R. Corbet, D. McKenna, et. al.
Wed, 14 Apr 2021
35/67

Comments: Accepted for publication in Animation Practice, Process & Production

The Phosphene Controversy: Is it Phosphene? Is there life on Venus? [CL]

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http://arxiv.org/abs/2104.01932


On 14th September 2020, the Royal Astronomical Society made an official statement coupled with a webminar on the discovery of phosphine on Venus. Single-line millimetre-waveband spectral detections of phosphine (with a signal-to-noise ratio of $\approx$ 15$\sigma$) from the JCMT and ALMA telescopes indicated a phosphine abundance of 20 ppb (parts per billion), 1000 times more than that on the Earth. Phosphine is an important biomarker and immediate speculation in the media about indicators of life being found on Venus followed. This article presents an analysis of the study and the results on the observation of the spectral absorption feature of phosphine in the clouds of Venus, thus implying as a potential biosignature. If phosphine is produced through biotic, as opposed to abiotic pathways, the discovery could imply a significant biomass in the Venusian atmosphere. The discovery led to a major controversy with criticism of the analysis and results and responses to it. The issue remains unresolved, leading to a fresh interest in the study of Venus including ground-based observations as well as space-probes that can answer these questions conclusively.

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P. Hasan
Tue, 6 Apr 2021
23/55

Comments: Published in Astrobiology Newsletter, 14(1), 4, 2021, DOI: 10.13140/RG.2.2.13819.23847

The secret of the elixir of youth of blue straggler stars [SSA]

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http://arxiv.org/abs/2103.16866


Using Gaia EDR3, we study the most spectacular and photogenic cluster of Ptolemy. After deriving its membership, we identify in its colour-magnitude diagram a star that definitively decided to straggle and dress in blue. Further analysis with the FARCE telescope allows us to discover in its light curve the secret of its rejuvenation, which we gladly share in this paper. This research is an important contribution to attain the ultimate goal of astronomy as professed by DJ Format.

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H. Boffin
Thu, 1 Apr 2021
11/71

Comments: Happy April Fool day!

I Knew You Were Trouble: Emotional Trends in the Repertoire of Taylor Swift [CL]

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http://arxiv.org/abs/2103.16737


As a modern musician and cultural icon, Taylor Swift has earned worldwide acclaim via pieces which predominantly draw upon the complex dynamics of personal and interpersonal experiences. Here we show, for the first time, how Swift’s lyrical and melodic structure have evolved in their representation of emotions over a timescale of $\tau\sim14$ yr. Previous progress on this topic has been challenging based on the sheer volume of the relevant discography, and that uniquely identifying a song that optimally describes a hypothetical emotional state represents a multi-dimensional and complex task. To quantify the emotional state of a song, we separate the criteria into the level of optimism ($H$) and the strength of commitment to a relationship ($R$), based on lyrics and chordal tones. We apply these criteria to a set of 149 pieces spanning almost the entire repertoire. We find an overall trend toward positive emotions in stronger relationships, with a best-fit linear relationship of $R=0.642^{+0.086}{-0.053}H-1.74^{+0.39}{-0.29}$. We find no significant trends in mean happiness ($H$) within individual albums over time. The mean relationship score ($R$) shows trends which we speculate may be due to age and the global pandemic. We provide tentative indications that partners with blue eyes and/or bad reputations may lead to overall less positive emotions, while those with green or indigo-colored eyes may produce more positive emotions and stronger relationships. However, we stress that these trends are based on small sample sizes, and more data are necessary to validate them. Finally, we present the taylorswift python package which can be used to optimize song selection according to a specific mood.

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M. Mansfield and D. Seligman
Thu, 1 Apr 2021
14/71

Comments: 11 pages, 8 figures. Submitted to Acta Prima Aprila. taylorswift code available at this http URL

The Existential Threat of Future Exoplanet Discoveries [CL]

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http://arxiv.org/abs/2103.17079


The last 25 years have been revolutionary in astronomy, as the field of exoplanets has gone from no known planets outside the Solar System to thousands discovered over the last year few years. This represents a rapid increase not just in known planets (often referred to as Mamajek’s Law), but also in total planetary mass. What has been heretofore unaddressed, however, is that this rapid increase in planetary masses may have disastrous consequences for the future of humanity. We look at how the number of planets, and more importantly, the mass of these planets has changed in the past and how we can expect this to change in the future. The answers to those questions, and how we respond to them, will determine if humanity is able to survive beyond the next 230 years.

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M. Lund
Thu, 1 Apr 2021
30/71

Comments: 7 pages, 3 figures. Submitted to Acta Prima Aprilia

From the SpaceX Starlink megaconstellation to the search for Type-I civilizations [CL]

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http://arxiv.org/abs/2103.07227


Here we extrapolate the idea of launching SpaceX’s Starlink satellites and study the possibility of building planetary megastructures (either designed as solid objects or as a web of satellites) by Type-I civilizations and the consequent detection of their techno-signatures. We have shown that the instruments of The Very Large Telescope Interferometer (VLTI) can potentially observe emission pattern of the huge constructions. Efficiency of the spectral variability method has been emphasized and the role of the FAST telescope was discussed.

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Z. Osmanov
Mon, 15 Mar 21
32/36

Comments: 5 pages, 0 figures

Triggering A Climate Change Dominated "Anthropocene": Is It Common Among Exocivilizations? [EPA]

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http://arxiv.org/abs/2103.06330


We seek to model the coupled evolution of a planet and a civilization through the era when energy harvesting by the civilization drives the planet into new and adverse climate states. In this way we ask if triggering “anthropocenes” of the kind humanity is experiencing now might be a generic feature of planet-civilization evolution. In this study we focus on the effects of energy harvesting via combustion and vary the planet’s initial atmospheric chemistry and orbital radius. In our model, energy harvesting increases the civilization’s population growth rate while also, eventually, leading to a degradation of the planetary climate state (relative to the civilization’s habitability.) We also assume the existence of a Complex Life Habitable Zone in which very high levels of $CO_2$ are detrimental to multi-cellular animal life such as those creating technological civilizations. Our models show that the civilization’s growth is truncated by planetary feedback (a “climate dominated anthropocene”) for a significant region of the initial parameter space.

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E. Savitch, A. Frank, J. Carroll-Nellenback, et. al.
Fri, 12 Mar 21
55/59

Comments: 19 pages, 13 figures

Oumuamua Is Not a Probe Sent to our Solar System by an Alien Civilization [CL]

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http://arxiv.org/abs/2103.05559


Oumuamua, the first known object of extrasolar origin seen to enter our Solar System, has multiple unusual characteristics that, taken together, are very difficult to explain with conventional astronomical entities like asteroids and comets. Consequently, it has been hypothesized that Oumuamua is an interstellar probe that was constructed by an alien civilization. We demonstrate that the accomplishments that can be achieved with large space telescopes/interferometers in the alien’s planetary system will completely quench any motivation for construction and launch of an Oumuamua-like probe. The absence of any such motivation proves that Oumuamua is not an alien creation.

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B. Zuckerman
Wed, 10 Mar 21
56/56

Comments: Submitted for publication in the AAS journals. The Zuckerman (1981) reference is available in pdf format on request to the author

Longevity is the key factor in the search for technosignatures [IMA]

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http://arxiv.org/abs/2103.02923


It is well-known that the chances of success of SETI depend on the longevity of technological civilizations or, more broadly, on the duration of the signs of their existence, or technosignatures. Here, we re-examine this general tenet in more detail, and we show that its broader implications were not given the proper significance. In particular, an often overlooked aspect is that the duration of a technosignature is in principle almost entirely separable from the age of the civilization that produces it. We propose a classification scheme of technosignatures based on their duration and, using Monte Carlo simulations, we show that, given an initial generic distribution of Galactic technosignatures, only the ones with the longest duration are likely to be detected. This tells us, among other things, that looking for a large number of short-lived technosignatures is a weaker observational strategy than focusing the search on a few long-lived ones. It also suggests to abandon any anthropocentric bias in approaching the question of extraterrestrial intelligence. We finally give some ideas of possible pathways that can lead to the establishment of long-lived technosignatures.

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A. Balbi and M. Ćirković
Fri, 5 Mar 21
19/64

Comments: Accepted for publication in The Astronomical Journal

`Oumuamua is not Artificial [CL]

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http://arxiv.org/abs/2102.07871


I summarize evidence against the hypothesis that `Oumuamua is the artificial creation of an advanced civilization. An appendix discusses the flaws and inconsistencies of the “Breakthrough” proposal for laser acceleration of spacecraft to semi-relativistic speeds. Reality is much more challenging, and interesting.

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J. Katz
Wed, 17 Feb 21
49/56

Comments: 8 pp

Minimal conditions for survival of technological civilizations in the face of stellar evolution [SSA]

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http://arxiv.org/abs/2102.05703


The ease of interstellar rocket travel is an issue with implications for the long term fate of our own and other civilizations and for the much-debated number of technological civilizations in the Galaxy. We show that the physical barrier to interstellar travel can be greatly reduced if voyagers are patient, and wait for the close passage of another star. For a representative time of $\sim$1 Gyr, characteristic of the remaining time that Earth will remain habitable, one anticipates a passage of another star within $\sim 1500$~AU. This lowers the travel time for interstellar migration by $\sim$ two orders of magnitude compared with calculated travel times based on distances comparable to average interstellar separations (i.e., $\sim$1 pc) in the solar vicinity. We consider the implications for how long-lived civilizations may respond to stellar evolution, including the case of stars in wide binaries, and the difficulties of identifying systems currently undergoing a relevant close encounter.
Assuming that life originates only around G-type stars, but migrates primarily to lower mass hosts when the original system becomes uninhabitable, the fraction of extant technological civilizations that exist as diaspora can be comparable to the fraction that still orbit their original host stars.

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B. Hansen and B. Zuckerman
Fri, 12 Feb 21
28/59

Comments: 9 pages, 0 figures, to appear in the Astronomical Journal