Christmas in the company of the first interstellar comet ever discovered

interstellar comet hubble
Hubble’s view of interstellar comet Borisov/2I
Credit: NASA, ESA, and D. Jewitt (UCLA)

It seems that the gift that Christmas wanted to give us this year goes far beyond expectations. On December 29th, the first interstellar comet discovered will pass to the minimum distance from Earth – 1.9 AU.

The first comet of interstellar origin 

Its name is C/2019 Q4 or 2I/Borisov. The second interstellar object ever observed, probably started from the planetary system of one of the multitudes of stars in the constellation of Cassiopeia.

The discovery marks therefore an important step for Astronomy. The only other object from interstellar space, was identified in 2017 – the asteroid ‘Oumuamua. The exotic name of the latter reminds us that the origin of these objects is outside our Solar System.

The comet 2I/Borisov

If the asteroid ‘Oumuamua was of completely alien origin, the comet Borisov has instead characteristics, like its color, that bind it to our Solar System.

Even its nucleus is similar to that of “our” asteroids. Studies are still in progress to determine their conformation, and therefore their origin.


Its main feature, of which we realized on September 8th, is its markedly hyperbolic orbit, unlike the comets coming from the Cloud of Oort, whose eccentricity is less. Therefore thanks to these observations it has been possible to say with certainty that Borisov is the second object of interstellar origin after the ‘Oumuamua.

When and how to observe it

Observable in the northern hemisphere, the comet will therefore reach the minimum distance from the Sun on December 8th. It will then approach the Earth on December 29th at a distance of 1.9 AU. Therefore the comet will be visible only with the help of telescopes, at least 15 cm in diameter – given its apparent magnitude of +16.

The discovery

Discovered on 30 August 2019 by Gennady Borisov, Ukrainian amateur astronomer. With a self-made telescope, Borisov observed the object signaling it to the Minor Planet Center. Many observers then mobilized, realizing the importance of the discovery made.

Hubble and the photograph of the interstellar comet

On October 12th the Hubble telescope took the comet again immortalizing it in the photograph you see in the article.

The fate of Borisov

The comet will travel to Jupiter leaving its orbit as early as mid-2020. It will then continue its journey into interstellar space – towards the constellation Telescope, visible in the southern hemisphere.


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