Just Visiting: An Interstellar Comet

Artist concept of Comet C-2017 U1 (PANSTARRS). Credit: Universe Sandbox / Bob Trembley

Having already made its closest approach to the Sun, comet C/2017 U1 is on its way back out of the solar system. Discovered only a few days ago on October 18, 2017, this comet is on an extremely hyperbolic trajectory, with the highest eccentricity (1.18) of any known comet.

Comet C-2017 U1 zoomed-out. Credit: JPL Small Body Browser.

Comet C-2017 U1 zoomed-in. Credit: JPL Small Body Browser.Credit: JPL Small Body Browser.

This comet may be the first clear case of an Interstellar comet: a comet that is not gravitationally bound to our Sun! The IAU Minor Planet Center is highly interested in having astronomers do follow-up observations on this comet.

At the time of this writing, no size or mass estimates for this comet were available.

Interactive Orbit Diagram for comet C/2017 U1 (Requires Java): Link

UPDATE: Follow-up observations with the Very Large Telescope (VLT) show that the object is not showing any cometary activity; it looks completely star-like. The object has been reclassified as an asteroid, and renamed to A/2017 U1.

For more information, read this Sky and Telescope article: Link