Our Solar System Has a New Visitor

A second interstellar visitor has entered our solar system, a comet known as 2I/Borisov. Unlike Oumuamua, the first interstellar object detected, 2I/Borisov seems to be an ordinary comet, very similar to the ones in our solor system.

In contrast to its predecessor, though, Borisov has been noticed on the inbound leg of its solar system sojourn. Researchers estimate it’ll make its closest approach to both the sun and Earth this December, before putting both in its rearview mirror and disappearing sometime next year. “Now we get a bit longer to watch it,” says Michele Bannister, a planetary astronomer at Queen’s University Belfast.

With just a handful of observations on Borisov under their belt, many scientists remain cautious. But so far, the preliminary results seem to support an intriguing idea: The comet’s extrasolar roots may be the most exotic thing about it.

Unlike ‘Oumuamua, it’s unquestionably a comet—one that bears a striking resemblance to those that originate in our own solar system, says Guzik, who, together with his colleagues, published a report on Borisov today in Nature Astronomy. The wayfaring rock sports all the necessary accoutrement for the classification, including a bright tail and a fuzzy, luminous halo called a coma—both byproducts of ice sublimating into gas under the sun’s heat. And with its reddish hue, it would blend seamlessly into a typical cometary lineup.