1I/'Oumuamua: The Nearest Exoplanet?
When
Where
Dr. Steve Desch
Professor, School of Earth and Space Exploration
Arizona State University
We have known for some time that our Solar System must have ejected trillions of comets in its youth, so we have long expected to see interstellar comets ejected from other systems pass through ours. The discoveries of 2I/Borisov and now 3I/ATLAS have confirmed that interstellar comets do routinely pass through our system. But when the first interstellar object, 1I/'Oumuamua, passed by Earth in October 2017, it defied expectations. It showed no dust coma or emission from CO or H2O, which would be expected for a comet. It did experience a non-gravitational acceleration away from the Sun that varied as 1/r2, like comets do; but instead of being ~0.01% the strength of gravity typical for most comets, it was ~0.1%. Many explanations, both natural and spaceshippy, were proposed; but none matched all the observations. In 2021 we showed that every observation of 'Oumuamua is consistent with it being nitrogen ice like that seen on the surface of Pluto, and similar to rare comets like C/2016 R2. Our solar system in its youth must have ejected many times more collisional fragments of Kuiper Belt Objects than comets. We interpret 'Oumuamua to most likely to have been ejected from an exo-pluto, less than half a billion years ago, possibly from an M dwarf system in the Perseus spiral arm of the Galaxy. The Vera Rubin Observatory is poised to discover many more interstellar objects like this in the next few years, allowing new direct observations of exoplanetary materials.
Host: Dr. Vishnu Reddy
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