With a staggering 500 trillion tons of mass and 137 kilometers across , C/2014 UN271 (Bernardinelli-Bernstein) has been confirmed by NASA’s Hubble Space Telescope to be the largest comet ever discovered.
“This is an amazing object, given how active it is when it’s still so far from the Sun,” said Man-To Hui, an astronomer at Macau University of Science and Technology and co-author of the paper. “We assumed that the comet could be quite large, but we needed the best data to confirm it.”
This confirmation has been possible thanks to new observations of the giant comet C/2014 UN271 (Bernardinelli-Bernstein) using the Hubble Space Telescope; proving what astronomers suspected from earlier data: that this object is indeed gigantic as far as frozen space rocks go.
The largest comet in the solar system
Due to its exceptional brightness, when its cometary nucleus was discovered in June 2021, it was already assumed that it must be a very large object from the Oort Cloud. The comet, named C/2014 UN271 (Bernardinelli-Bernstein) , was first discovered in 2010, but its size has not been confirmed until this study published in the Astrophysical Journal Letters.
The comet is currently too far away for Hubble to visually resolve its nucleus. Instead, the Hubble data shows a spike of bright light at the core’s location.
Its nucleus, the solid center of the comet, is about 50 times larger than the nucleus of most known comets, and is the largest NASA has ever seen. It is one hundred thousand times greater than the mass of a typical comet that is much closer to the Sun. It is headed for Earth, but for our peace of mind, NASA has assured us that it does not pose a threat to us.
“It will never get closer than 1.5 billion kilometers from the Sun, which is a little further than the distance of the planet Saturn. And that won’t be until the year 2031 ,” NASA said. (It will not approach more than 10.9 astronomical units – the distance between the Earth and the Sun).
These icy blocks are leftovers from the early days of planet building; they are among the oldest objects in the solar system. They were unceremoniously ejected from the solar system like a game of gravitational pinball between the massive outer planets. The ejected comets ended up in the Oort Cloud, a vast reservoir of distant comets that circles the solar system many billions of kilometers into deep space.
Comet C/2014 UN271 was discovered by astronomers Pedro Bernardinelli and Gary Bernstein in archival images from the Dark Energy Survey at the Cerro Tololo Inter-American Observatory in Chile.
It has a very dark core
The new Hubble measurements are in line with estimates from the Atacama Large Millimeter/submillimeter Array (ALMA), but strongly suggest that the core’s surface is darker than previously thought.
“It’s big and blacker than coal,” said Professor David Jewitt, an astronomer at the University of California, Los Angeles. “This comet is literally the tip of the iceberg of many thousands of comets that are too faint to see in the most distant parts of the solar system. We’ve always suspected that this comet had to be big because it’s so bright at such a great distance. Now we confirm that it is , ”concludes the expert.
The comet follows an elliptical orbit of three million years and has been falling inwards for more than 1 million years. At that distance, temperatures hover around -193°C, according to NASA.
Astronomers hope that the discovery of such a large comet will help shed light on the mysterious Oort Cloud.
Referencia: Man-To Hui et al. 2022. Hubble Space Telescope Detection of the Nucleus of Comet C/2014 UN271 (Bernardinelli-Bernstein). Astrophysical Journal Letters. 929, L12; doi: 10.3847/2041-8213/ac626a
