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A comet so huge it was first mistaken for a dwarf planet is on an inward path from the outer solar system.
There is no reason to worry – C / 2014 UN271 (Bernardinelli-Bernstein), as the comet is called, will not approach any closer to the Sun than just outside of Saturn’s orbit. But its large size and relative proximity will provide a rare opportunity to study a pristine Oort Cloud object and find new information about the formation of the solar system.
“We are privileged to have discovered perhaps the largest comet ever – or at least larger than any well-studied comet – and to have caught it early enough for people to see it evolve as it evolves. as it approaches and warms, ”co-discoverer and astronomer Gary Bernstein of the University of Pennsylvania said earlier this year.
“He hasn’t visited the solar system for over 3 million years.”
The outer solar system, on the whole, is a somewhat mysterious place. It’s very far away and quite dark, and the objects in it are quite small, so seeing what’s beyond Neptune’s orbit is quite difficult.
We have a general idea of the architecture of this region of space, with the Kuiper Belt made up of small icy bodies, then the Oort Cloud at much greater distances, but the details are harder to delve into.
However, we get more information from an unexpected source: the Dark Energy Survey (DES), which took place between August 2013 and January 2019.
He leaned over the southern sky in the infrared and near infrared for several hundred nights, studying objects such as supernovae and galaxy clusters, in an attempt to calculate the acceleration of the expansion of the Universe, thought to be influenced by dark energy.
The depth, breadth and accuracy of the survey were found to be very good at identifying objects in the Outer Solar System as well, beyond Neptune’s orbit about 30 astronomical units from the Sun. Earlier this year, a team of astronomers revealed they had discovered 461 previously unknown objects in the Outer Solar System in DES data.
One of these objects, spotted by Bernstein and his colleague University of Pennsylvania astronomer Pedro Bernardinelli, was C / 2014 UN271 (Bernardinelli-Bernstein). Now, they and their colleagues have described the comet in more detail in a preprinted document accepted in Letters from the astrophysical journal.
“We conclude that C / 2014 UN271 (Bernardinelli-Bernstein) is a “new” comet in the sense that there is no evidence of an earlier approach of more than 18 AU of the Sun since it was ejected into the Oort cloud, “the researchers write.
“Indeed, it may be the most pristine comet ever seen, as we detected it before it entered Uranus’ orbit, and it may be that she never did in any previous orbit. “
According to the team’s analysis, C / 2014 UN271 (Bernardinelli-Bernstein) began its journey inland at a distance of about 40,400 astronomical units from the Sun. It is right in the territory of the Oort Cloud, a huge sphere of icy objects that extends from about 2,000 to 100,000 astronomical units.
When it was discovered, the comet was at a distance of about 29 astronomical units from the Sun. Its closest approach to the Sun will be in 2031, when it reaches a distance of 10.97 astronomical units; Saturn’s orbit, for context, has an average distance of 9.5 astronomical units.
At a size of 155 kilometers (96 miles) in diameter, C / 2014 UN271 (Bernardinelli-Bernstein) is an absolute chonker, but even so, will not be visible to the naked eye at this distance.
However, scientists will take every opportunity to study it using telescopes. They hope that knowing more about its makeup can tell us more about the early solar system and its limitations.
This is because the icy rocks in the far fringes of our planetary system are believed to be more or less unchanged since their formation around 4.5 billion years ago. The volatiles locked in the ice of the comet should therefore contain information on the chemistry of the outer solar system during its formation.
Scientists have already spotted signs of coma, the comet atmosphere that appears when a comet approaches the Sun. The increasing heat sublimates the ices on the surface of the comet, producing the visible coma and, at closer distances, the cometary tails. Spectral analysis of these characteristics will tell us a lot about the content of C / 2014 UN271 (Bernardinelli-Bernstein).
As we know very little about the Oort Cloud and the objects therein, C / 2014 UN271 (Bernardinelli-Bernstein) represents a very rare window on this enigmatic region of our home in space.
The research was accepted in Letters from the astrophysical journal, and is available on arXiv.
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