NASA’s Hubble Space Telescope captured it. It was able to determine the size of its nucleus. It is no less than the largest comet ever seen. Its estimated diameter is about 128 kilometers across. Its nucleus is about 50 times larger than that of known comets.
This is the giant comet C/2014 UN271 (Bernardinelli-Bernstein). It is heading toward us at 35,400 kilometers per hour from the edge of the solar system. It will never get closer than 1,609 million kilometers from the Sun. Its mass is 500 billion tons.
“It’s the tip of the iceberg for thousands of comets too faint to see at great distances.” David Jewitt, professor of planetary science and astronomy at the University of California, stated. He is a co-author of the new study published in The Astrophysical Journal Letters. “We had always suspected that this comet had to be big. It’s very bright at a very large distance. Now we’ve confirmed that it is,” he added.
It was discovered in 2010 by astronomers Pedro Bernardinelli and Gary Bernstein. It happened at the Cerro Tololo Inter-American Observatory in Chile. Since then, it has been studied intensively by ground-based and space-based telescopes.
“This is an amazing object, given how active it is when it is still so far from the Sun. We needed these better data to confirm it,” said the paper’s lead author, Man-To Hui. He is with the Macau University of Science and Technology.
His team used Hubble to take five pictures of the comet on January 8, 2022. The challenge was how to discriminate the solid nucleus from the huge dusty coma that envelops it. The comet is too far away for its nucleus to be visually resolved by Hubble.
Hubble data show a bright spike of light. For this reason, Hui and his team made a computer model of the surrounding coma. They adjusted it to fit the telescope images. Then, the coma’s brightness was subtracted to leave the stellar nucleus behind, NASA explains. Thus it was learned that it is the largest comet ever seen.