Although comets can be distinguished by their flowing tails, which can extend for millions of miles, a comet’s core is its solid core. This core consists of ice and dust, forming a filthy snowball.
While most known comet cores are a few miles wide, astronomers using the Hubble Space Telescope have discovered comet C/2014 UN271 with a core that is 85 miles wide. That’s more than twice the width of Rhode Island.
This nucleus is about 50 times larger than that of other comets, and its mass is estimated at about 500 trillion tons, which is 100,000 times greater than the mass of a typical comet.
The comet is moving at 22,000 miles per hour from the edge of our solar system and will approach us in 2031. But it will never get closer than a billion miles from the sun — just a little further than the distance between Earth and Saturn.
Study co-author David Jewett, professor of planetary sciences and astronomy at the University of California, Los Angeles, said in a statement. “We have always suspected that this comet must be large because it is so bright at such a great distance. Now we confirm that it is.”
Comets are relics from the early days of the solar system, icy remnants from the time the planets formed. The gravity of the largest of the planets has pushed comets into the Oort cloud, and the cloud is now home to distant comets at the edge of our solar system that extends into deep space. Comets return toward the sun when their orbits are subjected to the gravitational pull of passing stars.
Within a few million years, the orbit of Comet Bernardinelli-Bernstein will return to the Oort cloud.
“This is amazing, given how active it is when it’s still far from the sun,” lead author Man Tu Hui, associate professor at the Macau University of Science and Technology in Taipa, Macau, said in a statement. “We thought the comet might be very large, but we needed the best data to confirm that.”
The research team used Hubble data to distinguish a comet’s nucleus from the coma, or the dusty envelope that surrounds a comet as it approaches the sun.
The sun’s heat warms the comet as it approaches, causing parts of it to sublimate, or go from a solid to a gas. This cloudy coma is the reason why comets appear so mysterious when we see them through telescopes.
Jewett said that the team’s analysis revealed not only the size of the core, but the fact that it is darker than coal.
The comet experiences an elliptical orbit of 3 million years in length. It is now less than two billion miles from our sun.
Astronomers hope that a study of Comet Bernardinelli-Bernstein will reveal more about the Oort cloud, which was first hypothesized by Dutch astronomer Jan Oort in 1950. The cloud remains theoretical because it is too far away to be observed, so the largest structure in our solar system is essentially invisible. .
NASA’s Voyager spacecraft won’t reach the inner Oort cloud for another 300 years — and it could take 30,000 years to pass through it. But every comet that approaches the Sun reveals more details about its mysterious home.