‘Oumuamua’s encounter with the inner solar system is dying down on Twitter, yet still it bristles with consequence and the uneasiness of unanswered questions. Why no coma?
Occam’s razor is a dull instrument that points almost unerringly to the mundane (as opposed to pointing to interstellar probes). One thus draws several conclusions. (1) ‘Oumuamua’s aspect ratio is substantially less than 10:1. (2) Billions of years in the interstellar environment lead to the buildup of a tarry crust that resists temporary heating, and this process is enhanced for comet-like planetesimals that form in systems with supersolar C/O ratios. (3) Most stars have true-Neptune analogs.
The resulting prediction is that slightly tweaked ongoing surveys, and soon LSST, should start turning up interstellar asteroids and perhaps interstellar comets with some frequency. If another one is found in the near-term, it would be interesting to look at the optimal mission designs that could accomplish an opportunistic sample-return.
From ‘Oumuamua’s perspective, the close encounter with the Sun was a near-indescribable stroke of luck. To scale, the stars of the galactic disk are like grains of sand separated by miles and crawling through space at a few feet per year. The Galaxy is the archetypal ...