Hyperbolic Comet SWAN

April 19, 2020:  Newly-discovered Comet SWAN (C/2020 F8) is shaping up to be a beauty. It looks great through small telescopes now, and could become visible to the naked eye next month. Gerald Rhemann sends this picture taken yesterday from Farm Tivoli, Namibia:

“The comet’s tail is almost a full degree long,” says Rhemann. “And it was an easy target for my 12-inch telescope at magnitude +7.5.”

Where does this beautiful comet come from? SWAN’s trajectory is an important clue. It’s falling toward the sun for the first time, and the sun’s gravity will probably slingshot Comet SWAN back into deep space. Comet SWAN may be a “hyperbolic comet“–that is, a comet whose orbit has an eccentricity greater than 1. Such comets come from the Oort Cloud or may even be interstellar.

The case for Comet SWAN being a hyperbolic comet is not ironclad. Based on an observation arc of only 3 days, JPL reports the eccentricity of SWAN’s orbit as 1.1 +/- 0.2.  The error bars are still large. The uncertainties will shrink, however, as more observations are added to the database in the nights ahead. Stay tuned for updates.

UPDATE (May 6, 2020): JPL has updated the comet’s eccentricity to 1.00095608 +/- 0.0011254 based on 18 days of data. It is definitely hyperbolic.

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