Alien Comet From Another Star System Has A ‘Dramatically Different’ Composition

by : Julia Banim on : 21 Apr 2020 11:12
Alien Comet From Another Star System Has A 'Dramatically Different' CompositionNASA

The first confirmed comet to enter our Solar System from another star system has scientists baffled by its ‘unusual’ composition.

The mysterious comet, called 2I/Borisov, was first spotted on August 30, 2019, by amateur astronomer Gennady Borisov. Being only the second known interstellar object ever to have passed through our Solar System, scientists were intrigued to learn more about its origins.


Now, new observations taken by NASA’s Hubble Space Telescope and the National Radio Astronomy Observatory’s Atacama Large Millimeter/submillimeter Array (ALMA) have revealed a little more about 2I/Borisov’s surprising chemistry.

Interstellar cometNASA, ESA and J. DePasquale (STScI)

According to NASA, 2I/Borisov contains a higher concentration of carbon monoxide than any other comet seen within an approximate 200 million miles (300 million kilometers) of our Sun.

Carbon monoxide is common in space as a gas, but will only form as ice only under the coldest conditions. The amount of carbon monoxide in this instance suggests 2I/Borisov was formed in a cold outer region of its solar system or around a star significantly cooler than our Sun.


This has led scientists to consider that the comet may have formed around a smaller, fainter type of star known as a red dwarf. However, other types of stars are still a possibility. Another theory is that 2I/Borisov could well be a carbon monoxide-rich piece of a small planet.

These findings have been published in two separate papers in Nature Astronomy, with both papers expressing surprise at the amount of carbon monoxide found in 2I/Borisov.

One paper details findings from a global team led by Martin Cordiner and Stefanie Milam from NASA’s Goddard Space Flight Center in Maryland, pointed the Chile-based ALMA at the comet on 15 and 16 December 2019.


While the other paper reports on findings by Dennis Bodewits and his colleagues at Alabama’s Auburn University, who were able to gather ultraviolet observations of the comet using the Hubble Space Telescope (HST) and the Neil Gehrels Swift Observatory.

Cordiner said:

This is the first time we’ve ever looked inside a comet from outside our solar system, and it is dramatically different from most other comets we’ve seen before.


He added:

If the gases we observed reflect the composition of 2I/Borisov’s birthplace, then it shows that it may have formed in a different way than our own solar system comets, in an extremely cold, outer region of a distant planetary system.

2I/Borisov’s unexpected chemistry could suggest a greater diversity of carbon monoxide in comets in our own solar system than had previously been realised.


As 2I/Borisov continues on its path through and out of the solar system, astronomers expect ever advancing technology will allow them to detect more interstellar objects in the future.

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Julia Banim

Jules studied English Literature with Creative Writing at Lancaster University before earning her masters in International Relations at Leiden University in The Netherlands (Hoi!). She then trained as a journalist through News Associates in Manchester. Jules has previously worked as a mental health blogger, copywriter and freelancer for various publications.

Topics: Science, Asteroid, NASA, Solar System, Space


Nature Astronomy and 2 others
  1. Nature Astronomy

    Unusually high CO abundance of the first active interstellar comet

  2. NASA

    Interstellar Comet Borisov Reveals Its Chemistry and Possible Origins

  3. Nature Astronomy

    The carbon monoxide-rich interstellar comet 2I/Borisov