A giant comet is expected in 2031

Bigger than Hale-Bopp, the record-breaking comet has just been discovered by scientists at Penn State University. It can be studied for another 10 years

Illustration of what Comet UN271 could look like in the Outer Solar System (image: NOIRLab / NSF / AURA / J. Da Silva)

In the late 1990s, the cometa Hale-Bopp it had illuminated the earth’s sky for 18 months, surpassing all records in terms of permanence in the earth’s orbit, amplitude and brightness. With a diameter of 60 kilometers, in fact, she was entitled to the primacy of the largest comet and luminous of the Solar System, at least until a few days ago. But now there is a new contender: astronomers from Penn State University in Pennsylvania have just discovered 2014 UN271, a new comet which, with a diameter of 100 kilometers, will reach the closest point to Earth in the 2031. He probably won’t replicate the same records as Hale-Bopp, though.

Comets are celestial bodies as old as the Sun, consisting mainly of reyes covered with ice, which come from a remote region of the Solar System called “nube di Oort“. It may happen that a rocky body exits the Oort cloud and approaches the Sun at great speed, entering an orbit from elliptical shape very elongated: it has become one Kite. When it approaches a few hundred million kilometers from the Sun, part of the ice layer is vaporized, giving the comet the classic shape with a rocky core it’s a elongated cloud of gas and dust. A comet usually travels in a closed orbit around the Sun, and reappears in the terrestrial skies periodically: in the history of human beings, the passage of comets has often been interpreted as sign of doom. This was not the case for the highly anticipated Hale-Bopp comet, and it certainly won’t be for UN271 either.

Giant kite
Image of the discovery of comet UN271. Credit: Dark Energy Survey / DOE / FNAL / DECam / CTIO / NOIRLab / NSF / AURA / P. Bernardinelli & G. Bernstein (UPenn) / DESI Legacy Imaging Surveys

An unexpected discovery

The comet was identified in images taken between 2014 and 2018 from telescope positioned in Chile of the research project Dark Energy Survey, the purpose of which is to map distant galaxies and exploding stars for investigate the accelerated expansion of the universor. The project databases, among other observations, counted at least 800 new frozen rock bodies, with orbits larger than that of Neptune. But one of these, the 2014 UN271, it was definitely unexpected. “It was by far the most interesting we found“, he has declared Pedro Berardinelli, one of the discoverers of the comet, to the New York Times. Following further observations with other telescopes, this time located in South Africa, confirmation has arrived: UN271, with its core and its tail of gas, it is a comet, and has been renamed Comet C/2014 UN271 (Bernardinelli-Bernstein), named after Bernardinelli and his other discoverer, Gary Bernstein.

Of UN271, what amazed the astronomers the most are precisely the size: scientists have estimated a diameter of 100 kilometers, much larger than the Hale-Bopp comet. More, the orbit of the comet it is very elongated, with a trajectory that goes from Saturn up to one light year from the Oort cloud: it is estimated that, to complete a lap full around the Solar System, the comet takes over 600 thousand years. We won’t see it again for a while, but UN271 will stay in our skies long enough to study it in depth: according to experts’ calculations, the comet will reach the closest point to Earth in 2031. However, if a second Hale-Bopp is expected, we are misleading: precisely because outside the orbit of Saturn, the comet will not be visible to the naked eye, but only with a good telescope.

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