Astronomers have detected Comet Borisov (C/2019 Q4), the second interstellar minor body to enter the solar system. First, there was 'Oumuamua, discovered nearly two years ago. Now we might be in store for another interstellar flyby, this time by the recently discovered comet.
Astronomers have almost certainly detected a second interstellar comet, but there is yet a lot of work to be done to find out more about this alien space rock.
After getting enough data, I suspect 'we'll be assigning a permanent designation to say this object is interstellar. - Davide Farnocchia
Gennady Borisov captured the object on August 30, 2019, at the MARGO Observatory near Nauchnij, Crimea when it was about three astronomical units (a.u.) from the Sun.
As Comet Borisov is anticipated to approach both the Sun and the Earth, its brightness is also expected to increase from the current magnitude of 17 to about 15 when closest to the Earth on December 28 UT. The comet has a slightly reddish surface that resembles that of our own solar system's long-period comets, two recent are: comets Hale-Bopp (1997), and Hyakutake (1996).
Additionally, 'it's going super fast: about 93,000 miles per hour (150,000 kilometers per hour), which is faster than any object from the outer fringes of our neighborhood would be traveling. As NASA and an international team of experts announced last week, the signs all point to it passing through our Solar System on its way from some distant origin.
Until very recently, astronomers had never spotted an interstellar comet, despite the fact that these extrasolar objects are thought to visit our Solar System all the time.