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Systemic - Characterizing Extrasolar Planetary Systems

Interstellar Asteroids

5 Nov 2017, 23:02 UTC
Interstellar Asteroids
(200 words excerpt, click title or image to see full post)

This was no fruit of such worlds and suns as shine on the telescopes and photographic plates of our observatories. This was no breath from the skies whose motions and dimensions our astronomers measure or deem to vast to measure. It was just a colour out of space — a frightful messenger from unformed realms of infinity…
Aww, come off it.
Wild-eyed extravagances aside, A/2017 U1 — the asteroid-like visitor from interstellar space — is an extraordinary object. In traversing the interstellar gulfs, its next encounter with a star that is as close as last month’s encounter with the Sun likely won’t occur for another quadrillion years, and so the mere fact that it zipped through suggests that quite a few interstellar asteroids are out there. And this, in turn, has some remarkable consequences. A straightforward cross-section based estimate suggests that the galaxy contains of order a hundred billion earth masses of A/2017 U1-like planetesimals. Hot Jupiters, terrestrial planets, and super-Earths are all incapable of using gravity-assist to eject bodies out of their parent systems, leaving the strong hint that as-yet undetected Neptune-like planets must be extremely common.
In general, extrapolations from a sample size of one don’t have ...

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