
Astronomers Spot First-Known Interstellar Comet - johnny313
http://www.skyandtelescope.com/astronomy-news/astronomers-spot-first-known-interstellar-comet/
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diggernet
"Based on its apparent brightness, dynamicist Bill Gray calculates that it
would have a diameter of about 160 meters (525 feet) if it were a rock with a
surface reflectivity of 10%."

It is, of course, almost certainly a rock. But as a pointless mental exercise,
how large would it be if it were a shiny metal probe?

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softrock
The observations are still coming in and things are very uncertain. One
astronomer on twitter noted that if the most uncertain measurement were
removed that the comet has a 0.9 eccentricity, and therefore likely not an
interstellar comet.

