File:Borisov Swings Past Sun.png

English: When astronomers see something in the universe that at first glance seems like one-of-a-kind, it's bound to stir up a lot of excitement and attention. Enter comet 2I/Borisov. This mysterious visitor from the depths of space is the first identified comet to arrive here from another star. We don't know from where or when the comet started heading toward our Sun, but it won't hang around for long. The Sun's gravity is slightly deflecting its trajectory, but can't capture it because of the shape of its orbit and high velocity of about 100 thousand miles per hour.

Telescopes around the world have been watching the fleeting visitor. NASA's Hubble Space Telescope has provided the sharpest views as the comet skirts by our Sun. Since October the space telescope has been following the comet like a sports photographer following horses as they speed around a racetrack. Hubble revealed that the heart of the comet, a loose agglomeration of ices and dust particles, is likely no more than about 3,200 feet across, about the length of nine football fields. Though comet Borisov is the first of its kind, no doubt there are many other comet vagabonds out there, plying the space between stars. Astronomers will eagerly be on the lookout for the next mysterious visitor from far beyond.

The comet appears in front of a distant background spiral galaxy (left). The galaxy's bright central core is smeared because Hubble was tracking the comet. Comet Borisov was approximately 203 million miles from Earth in this image.

Read more: go.nasa.gov/34bLzhn

Credit: NASA, ESA and D. Jewitt (UCLA)