Diagram of the path of C/2017 U1 PanSTARRS, a possible interstellar comet spotted on Oct. 18, 2017. (NASA/JPL)
On October 14, 2017, what appears to be a comet sped past Earth at a distance of about 15 million miles after swinging around the Sun. It had come within 23.4 million miles of our home star over a month earlier on Sept. 9, and in fact wasn’t spotted by astronomers until Oct. 18—four days after its closest pass by us.
Further observations showed that the approximately 525-foot-wide object (an estimate based on its reflectivity) first approached traveling 16 miles a second from the direction of the constellation Lyra—quite a high angle from the plane of the rest of the Solar System—and is on a hyperbolic trajectory, moving quickly enough both in- and outbound along its course to permanently escape the Sun’s gravity…unlike any other comet ever observed.
Named C/2017 U1 PanSTARRS (after the Pan-STARRS telescope in Maui which was used to first identify it) the object may be, based on its behavior, the first interstellar comet ever seen—a visiting world from completely outside our Solar System.
Read more and see an image of the comet on Sky & Telescope here. Tagged: ...