New observations of comet C/2014 UN271 Bernardinelli-Bernstein, which is currently heading into the inner Solar System, suggest that its core is about 150 km long wide. It is therefore officially the largest comet ever discovered.
Also known as Comet Bernardinelli-Bernstein, Comet C/2014 UN271 was identified in Dark Energy Survey data captured between 2014 and 2018. on its power of luminosity, the astronomers quickly understood that this object integrated the "court of the big ones". It was then estimated that its nucleus could measure at least 100 km in diameter. In reality, we underestimated its size, mainly due to its remoteness. At the time of these first observations, C/2014 UN271 was indeed more than 29 astronomical units (AU) from the Sun, almost as far as Neptune.
The object has since moved closer. On June 23, New Zealand astronomers even spotted a coma, a halo of gas and dust released under the effect of stellar heat, causing the sublimation of the ice in its core. The comet was then about 19 AU from the Sun.
The researchers also took the opportunity to refine their estimates. New analysis suggests comet's nucleus is about 150km wide , again based on its luminosity. This makes it the largest comet ever discovered, by far! Indeed, the previous record was held by comet Sarabat of 1729, with a nucleus estimated at about 100 km wide. Typically, these objects are much smaller, providing "seeds" a few tens of kilometers in diameter.
As part of this work, the results of which were submitted to the Astrophysical Journal Letters, the team also specified the orbit of the comet. According to these calculations, the object makes an incredibly long round trip leading it to more than 40,000 AU from the Sun . The last time the comet was at its furthest point was about 1.5 million years ago .
We also know that the last time it passed through our neighborhood was approximately 3.5 million years ago . At the time, it had approached less than 18 AU from the Sun . For this new passage through the Solar System, the comet will come even closer (at 10.9 AU in 2031), almost reaching the orbit of Saturn. Astronomers are obviously impatient to be able to observe this object from the confines of the Solar System (Oort cloud) more closely.
