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An interstellar comet revealed

Comet 2I/Borisov
Comet 2I/Borisov. Photo: Gemini Observatory/NSF/AURA

The interstellar comet discovered in August looks very similar to comets originating in our own solar system, according to a new study in Nature Astronomy this week.

The big picture: Comet 2I/Borisov represents just the second-known interstellar object to make its way through our solar system, and it's astronomers' best chance so far to study a piece of a distant star system at close range.

  • Even if it does turn out that the comet is just like those native to our solar system, it will show astronomers that other planetary systems light-years from our own likely formed in similar ways.

What they found: Unlike the strange cigar shape of the first interstellar object — named 'Oumuamua and seen in 2017 — 2I/Borisov has a pronounced dust tail and a reddish color that can be compared to other comets, according to the study.

  • "In combination with what we have learned from peculiar `Oumuamua, it tells us that there may be a lot of diversity in other planetary systems and the formation of minor bodies," Piotr Guzik, one of the authors of the new study, told Axios via email.
  • The team began its observations of the comet on Sept. 10, using the Gemini North Telescope in Hawaii and the William Herschel Telescope in Spain.
"This is a quick first look at the object and is showing what everyone has seen who has been observing this."
— University of Hawaii astronomer Karen Meech, who did not take part in the study, told Axios via email

What to watch: Astronomers will be keeping a close eye on 2I/Borisov as long as it's visible from Earth.

  • An earlier study submitted to The Astrophysical Journal Letters found cyanogen, a common molecule in solar system comets, in 2I/Borisov's atmosphere.
  • However, the comet still isn't in the perfect position to be able to get a good look at its chemical signature yet.
  • As the object gets closer — with its closest flyby of the Sun expected in early December — scientists should be able to piece together the chemical makeup of the comet's atmosphere and figure out just how familiar or alien it really is.