"Comet - C/2019 Q4 (Borisov) - Artist Concept" by NASA / Public Domain

How Does the New Interstellar Object Differ From ‘Oumuamua?

Sep 18, 2019

By Ryan F. Mandelbaum

The second interstellar object on record has visited our solar system, according to astronomical observations made in recent week. But how does this new visitor differ from ‘Oumuamua, the first interstellar object?

Scientists have been eager to learn more about Comet C/2019 Q4 (Borisov) since amateur astronomer Gennady Borisov first spotted it on August 30. Follow-up observations determined found that its orbit suggests it originated from outside the solar system. A comparison to the first interstellar object, ‘Oumuamua, could provide an interesting perspective on what these objects are like generally.

Astronomers discovered the first interstellar object on record, 1I/2017 U1 ‘Oumuamua, on October 19, 2017, and were able to gather hundreds of observations of the object as it whizzed through the solar system. It was strangely cigar-shaped, and seemed to accelerate as it traveled away from the Sun. There has been some wild conjecture as to its origin and the cause of its acceleration (“aliens!”), but less speculative debate has centered around whether the object is more like a rocky asteroid or a comet that released some gas and accelerated as the Sun heated it up. Observations haven’t seen evidence of a cometary-like tail, but “a volatile-rich gas-venting structure for ‘Oumuamua provides the simplest explanation for its odd trajectory,” according to a paper in The Astrophysical Journal.

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