Sep 17, 2019 - Science

Astronomers giddy about 2nd interstellar object in 2 years

Illustration: Aïda Amer/Axios

Astronomers have now spotted a second mysterious, likely interstellar object on a path through our solar system.

Why it matters: These interlopers — the first of which came through the inner solar system in 2017 — represent the best chance astronomers have so far of learning more about far off star systems from close range.

  • "This is the only thing in astrophysics where you have a piece of the galaxy come to you," planetary astronomer Michele Bannister told Axios.

What's happening: Last week, scientists announced the discovery of a likely interstellar comet.

  • NASA right now predicts the comet will fly about 190 million miles from the Sun during close approach in December before heading out of the solar system again.
  • Unlike 'Oumuamua, the first interstellar object, this comet — C/2019 Q4 (Borisov) — will be visible for about a year, giving astronomers time to study its structure, composition and path through the galaxy.

Details: Some scientists will be focused on the comet's atmosphere, known as a coma, that is created when the object heats up as it nears the Sun. The heat causes ice on the comet to turn immediately from a solid to gas.

  • Scientists hope to piece together what kinds of ice exist on the comet — and the amount — by watching how sunlight hits the coma.
  • Early results from observations taken by the Gran Telescopio Canarias show that C/2019 Q4's composition may be similar to the comets seen in our solar system.
  • If the comet's chemistry matches what astronomers have found in comets elsewhere in our solar system, it could indicate that the part of space where the comet formed might be similar to our solar system's chemistry.
"This, to me, has bearing on, 'Are all solar systems suitable to life?'"
Karen Meech, an astronomer at the University of Hawaii, told Axios

Background: Scientists are hoping to compare 'Oumuamua and C/2019 Q4 to figure out just how different or similar the 2 objects coming from 2 parts of the galaxy are.

  • In particular, they'll attempt to compare C/2019 Q4's shape to the odd cigar-like structure of 'Oumuamua, which looked different from anything we've yet seen in our solar system.

What's next: Some scientists hope to create a protocol for whenever the next interstellar comet is found in order to maximize their chances to observe it as soon as it's seen.

  • The Large Synoptic Survey Telescope, expected to come online next year, should be able to spot interstellar objects as they fly through our solar system.
  • The European Space Agency's Comet Interceptor mission — expected to launch in 2028 — could intercept an interstellar comet when it's in place and ready after its expected launch in 2028.

The big picture: Even without those new tools online, catching sight of C/2019 Q4 just 2 years after seeing 'Oumuamua already deepens the mystery around just how many of these interstellar objects might be visiting our solar system.

  • It's possible these objects pass through our solar system more often than scientists originally thought, but with just 2 seen so far scientists can't say whether that's definitively the case or not.
  • "Maybe our understanding is different. Maybe we're just super lucky. Maybe there's a new mystery here. We don't know," space scientist Carrie Nugent told Axios.
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