A huge comet with a core size of around 137 kilometres (85 miles) is approaching the boundaries of our solar system at 35,400 kilometres per hour. Fortunately for us, this comet, C/2014 UN271 (Bernardinelli-Bernstein Comet), is not destined to enter the interior of our system and become an "elephant in a china shop". The closest point of its orbit, which the comet will reach in 2031, is at a distance of 1.61 billion kilometres from the Sun, just beyond the orbit of Saturn.
We remind our readers that comets are the oldest objects in our solar system. They are icy bodies, which periodically are "pulled" by gravitational interactions of outer circle planets from a storehouse of primordial material, the cloud of Oort surrounding our Solar system, which border passes at a distance of 50-100 thousand astronomical units from the Sun.
Traditional comets, when approaching the Sun, extend their tail, which is many millions of kilometres long, which makes them look like a cosmic "signal rocket". However, this tail is formed by the evaporation of the comet's nucleus, which is a mixture of ice, dust and rocks, and the size of the nucleus of comet C/2014 UN271, as mentioned above, is 137 kilometres, which was determined with the Hubble Space Telescope. At this size, the nucleus of the comet C/2014 UN271 has a mass of 500 trillion tons, which is at least 50 times the mass of the nucleus of any other known comet.
Note that the comet C/2014 UN271 was first observed by astronomers Pedro Bernardinelli (Pedro Bernardinelli) and Gary Bernstein (Gary Bernstein) in 2010, when it was at a distance of 4.8 billion kilometres from the Sun. The comet is now 3.2 billion kilometres away, and will be back home in the Oort Cloud by 2031, when it will have passed its closest point to the Sun.
The study of comet C/2014 UN271 has been ongoing since its discovery, and the biggest problem has been that at long range it has been virtually impossible to separate images of the comet's nucleus from the coma, the cloud of gas and dust that envelops the nucleus. But on 8 January 2022, the Hubble Space Telescope took a series of five images, which were later complemented by data from the ALMA (Atacama Large Millimeter/submillimeter Array) radio telescope. The resulting data set made it possible not only to measure the size of the comet's nucleus, but also to determine several other characteristics, including the colour of the nucleus' surface.
"This comet is very large and its surface is blacker than coal," the researchers write.