http://arxiv.org/abs/2210.02338
The aging and gradual brightening of the Sun will challenge Earth’s habitability in the next few billion years. If life exists elsewhere in the Universe, the aging of their host star will similarly pose an existential threat. One solution to this threat, which we dub a Lazarus star, is for an advanced civilization to remove (or “star-lift”) mass from their host star at a rate which offsets the increase in luminosity, keeping the flux on the habitable planet(s) constant and extending the lifetime of their star. While this idea has existed since 1985 when it was first proposed by Criswell, numerical investigations of star-lifting have been lacking. Here, we use MIST evolutionary tracks to find mass vs. age and $\dot{M}$ vs. age relations with initial mass ranging from $0.15{-}1.3 {\rm M}{\odot}$. We do this for two different implementations of star-lifting, isoluminosity and isoirradiance, where both hold the incident flux on the habitable planet(s) constant, but the former keeps the orbital radius constant and the latter accounts for a changing orbital radius. We reveal two distinct behaviours for these Lazarus stars. For most stars initially below ${\sim} 0.3 {\rm M}{\odot}$, we find that their lifetimes can be gradually extended until their mass reaches 0.1${\rm M}{\odot}$, approaching the hydrogen burning limit – with a lifetime of many trillions of years. In contrast, for more massive stars, their natural evolution causes them to leave the main sequence before reaching the hydrogen burning limit. For example, the Sun has a main-sequence lifetime which can be increased by 10 (6) Gyrs if we started star-lifting for isoluminosity (isoirradiance) today. This requires a mass loss rate of ${\sim}0.02 {\rm M}{\mathrm{Ceres}}$ per year. We compare star-lifting to other survival strategies and briefly discuss methods for detecting these engineered stars.
M. Scoggins and D. Kipping
Thu, 6 Oct 22
47/77
Comments: 8 pages, 5 figures