Its icy core is larger than any other we have ever seen – it is about 80 miles in diameter and 50 times larger than the heart of the most famous comets. It is also estimated to have a mass of about 500 trillion tons – a hundred thousand times larger than the typical comet closest to the Sun. And the object, known as C / 2014 UN271 (Bernardinelli-Bernstein), is heading in that direction, fast. Traveling at 22,000 miles per hour, it moves from the edge of the solar system to its center. However, we must be completely safe. The comet will not approach more than a billion miles from the Sun – even further away from the planet Saturn – and this will not happen until 2031. The object has been known since November 2010, when it was 3 billion miles from the Sun or the distance from Poseidon. Since then, researchers have been trying to find out more about it, using telescopes both in space and on Earth. As part of this research, scientists used NASA’s Hubble Space Telescope to calculate the comet’s size and revealed its enormous size. The researchers thought that the comet must be at least large enough, given how active it is even at such a great distance from the Sun. But the new data came from five photos taken earlier this year by Hubble. However, measuring size is not as simple as taking these pictures. Scientists have to distinguish the solid nucleus in the middle from the large dusty coma that surrounds it, and it is too far away for the images to be clear enough to tell the difference. Instead, scientists examined the bright dot of light that marked the nucleus in the comet’s heart. Then they made a computer model of the coma that would surround it and adapted it according to the pictures. (Nasa) Overall, these images made it possible to understand the size. The researchers were able to remove the glow of the coma and leave behind only the solid nucleus. The data also reveal more about the comet when combined with other radio observations received from the ALMA telescope in Chile. The sizes were the same, but the data suggest that the comet’s surface is darker than previously thought – with one researcher describing the object as “large and blacker than carbon”. The comet is billions of years old and as such represents a relic from the first days of our solar system. It originated in the Oort Cloud on the edge of our planetary neighborhood and falls back to our Sun for at least a million years. Oort Cloud comets are believed to have started their lives much closer to our star. But in its early days, they were thrown to the edges of the solar system during the most chaotic early days of the solar system, when the vast outer planets were still in orbit. The new record-breaking object could help us better characterize this Oort Cloud, which is 5,000 times as far from our Sun as we are and is so difficult to see immediately that it remains theoretical. By studying Comet Bernardinelli-Bernstein, researchers can better understand how objects grow in this distant cloud, for example – and how big they could be. The findings are reported in a new paper, “Hubble Space Telescope Detection of the Nucleus of Comet C / 2014 UN271 (Bernardinelli-Bernstein)”, published in The Astrophysical Journal Letters.
