1I/`Oumuamua as a Tidal Disruption Fragment From a Binary Star System [EPA]


1I/Oumuamua is the first known interstellar small body, probably being only about 100 m in size. Against expectations based on comets,Oumuamua does not show any activity and has a very elongated figure, and also exhibits undamped rotational tumbling. In contrast, Oumuamua's trajectory indicates that it was moving with the local stars, as expected from a low-velocity ejection from a relatively nearby system. Here we assume thatOumuamua is typical of 100-m interstellar objects, and speculate on its origins. We find that giant planets are relatively inefficient at ejecting small bodies from inner solar systems of main-sequence stars, and that binary systems offer a much better opportunity for ejections of non-volatile bodies. We also conclude that Oumuamua is not a member of a collisional population, which could explain its dramatic difference from small asteroids. We observe that 100 m small bodies are expected to carry little mass in realistic collisional populations, and that occasional events when whole planets are disrupted in catastrophic encounters may dominate interstellar population of 100 m fragments. Unlike the Sun or Jupiter, red dwarf stars are very dense and are capable of thoroughly tidally disrupting terrestrial planets. We conclude that the origin ofOumuamua as a fragment from a planet that was tidally disrupted and then ejected by a dense member of a binary system could explain its peculiarities.

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M. Cuk
Wed, 6 Dec 17

Comments: Submitted to ApJL