The largest comet ever seen by Hubble Space Telescope is hurtling towards Earth. This behemoth has a diameter of 80 miles (129 km) across, with a nucleus 50 times bigger than normal, which according to NASA, makes it larger than the state of Rhode Island. The icy nucleus has a mass of about 500 trillion tonnes, a hundred thousand times greater than the mass of a typical comet found much closer to the Sun.
The comet known as C/2014 UN271 (Bernardinelli-Bernstein) is barreling our way at 22,000 miles per hour (35,406 km/h) from the edge of the solar system. There is no need to panic however, because it will “never get closer than 1 billion miles away from the Sun, which is slightly farther than the distance of the planet Saturn”, according to NASA. “And that won’t be until 2031.”
“This comet is literally the tip of the iceberg for many thousands of comets that are too faint to see in the more distant parts of the solar system,” said David Jewitt, a professor of planetary science and astronomy at the University of California, Los Angeles (UCLA), and co-author of the new study in The Astrophysical Journal Letters. “We’ve always suspected this comet had to be big because it is so bright at such a large distance. Now we confirm it is.”
The previous record holder was comet C/2002 VQ94, with a nucleus estimated to be 60 miles across, discovered in 2002.
According to the statement, “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 was first serendipitously observed in November 2010, when it was a whopping 3 billion miles from the Sun, which is nearly the average distance to Neptune. Since then, it has been intensively studied by ground and space-based telescopes.”
And now Hubble has finally determine its size!
“This is an amazing object, given how active it is when it’s still so far from the Sun,” said the paper’s lead author Man-To Hui of the Macau University of Science and Technology, Taipa, Macau. “We guessed the comet might be pretty big, but we needed the best data to confirm this.” So, his team used Hubble to take five photos of the comet on January 8, 2022.
Because the comet is currently too far away, it was a challange to differentiate its solid nucleus from the dusty coma enveloping it. (What is the differences between comets, asteroids and meteors?)
As per the statement, “The comet is currently too far away for its nucleus to be visually resolved by Hubble. Instead, the Hubble data show a bright spike of light at the nucleus’ location. Hui and his team next made a computer model of the surrounding coma and adjusted it to fit the Hubble images. Then, the glow of the coma was subtracted to leave behind the starlike nucleus. Hui and his team compared the brightness of the nucleus to earlier radio observations from the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. This combined data constrains the diameter and the reflectivity of the nucleus. The new Hubble measurements are close to the earlier size estimates from ALMA, but convincingly suggest a darker nucleus surface than previously thought.”
“It’s big and it’s blacker than coal,” said David Jewitt.
Comet Bernardinelli-Bernstein has been falling toward the Sun for over 1 million years, from the Oort Cloud (the hypothesized nesting ground of trillions of comets first suggested by Dutch astronomer Jan Oort in 1950).
“The Oort Cloud’s comets didn’t actually form so far from the Sun; instead, they were tossed out of the solar system billions of years ago by a gravitational “pinball game” among the massive outer planets, when the orbits of Jupiter and Saturn were still evolving. The far-flung comets only travel back toward the Sun and planets if their distant orbits are disturbed by the gravitational tug of a passing star – like shaking apples out of a tree.”, says the NASA statement. Further adding, “Comet Bernardinelli-Bernstein follows a 3-million-year-long elliptical orbit, taking it as far from the Sun as roughly half a light-year. The comet is now less than 2 billion miles from the Sun, falling nearly perpendicular to the plane of our solar system. At that distance temperatures are only about minus 348 degrees Fahrenheit (176 Celsius). Yet that’s warm enough for carbon monoxide to sublimate off the surface to produce the dusty coma.”
Comet Bernardinelli-Bernstein’s size provides clues to the size distribution of comets in the Oort Cloud and hence its total mass. Estimates for the Oort Cloud’s mass vary widely, reaching as high as 20 times Earth’s mass.
“Circumstantial evidence come from infalling comets that can be traced back to this nesting ground. They approach the Sun from all different directions meaning the cloud must be spherical in shape. These comets are deep-freeze samples of the composition of the early solar system, preserved for billions of years. The reality of the Oort Cloud is bolstered by theoretical modeling of the formation and evolution of the solar system. The more observational evidence that can be gathered through deep sky surveys coupled with multiwavelength observations, the better astronomers will understand the Oort Cloud’s role in the solar system’s evolution.”
What a treasure the Hubble Space Telescope is. After over 30 years of service, it is still helping us solve the mysteries of the Universe!
Saima Baig
I am a Chartered Environmentalist from the Royal Society for the Environment, UK and co-owner of DoLocal Digital Marketing Agency Ltd, with a Master of Environmental Management from Yale University, an MBA in Finance, and a Bachelor of Science in Physics and Mathematics. I am passionate about science, history and environment and love to create content on these topics.
