Credit: NASA, STScI, D. Jewitt (UCLA), and K. Meech (University of Hawaii)

Astronomers using NASA's Hubble Space Telescope have found that the interstellar comet 2I/Borisov is providing the first glimpse of another star system's planetary building blocks.

The comet's unusual abundance of carbon monoxide is largely unlike comets belonging to our solar system. Borisov is the first known comet to originate from a different star system than our own. Researchers say its unusual composition points to a likely birthplace of a circumstellar disk around a cool red dwarf class of star. These observations are the first opportunity ever to sample the chemistry of the material in such a primordial disk around another star.

Comets are condensed samples of gas, ice, and dust that form swirling in the disk around a star during the birth of its planets. Studying comets is important because astronomers are still trying to understand the role they play in the buildup of planets. They can also redistribute organic material among young planets, and may have brought water to the early Earth. These activities are likely happening in other planetary systems, as demonstrated by Borisov's makeup.

"With an interstellar comet passing through our own solar system, it's like we get a sample of a planet orbiting another star showing up in our own back yard," said John Noonan of the Lunar and Planetary Laboratory at the University of Arizona, Tucson, who is a member of the Hubble research team led by Dennis Bodewits of Auburn University in Alabama.

The team used Hubble's unique ultraviolet sensitivity to spectroscopically detect carbon monoxide gas escaping from comet Borisov's solid comet nucleus. Hubble’s Cosmic Origins Spectrograph observed the comet on four separate occasions, from Dec. 11, 2019 to Jan. 13, 2020, which allowed the researchers to see the object's chemical composition change quickly, as different ice mixtures, including carbon monoxide, oxygen, and water, sublimated under the warmth of the Sun.

The Hubble astronomers were surprised to find that

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