The huge comet is called C / 2014 UN271, otherwise known as the Bernardinelli-Bernstein comet, and flies to Earth at 22,000 miles per hour from the edge of the solar system. NASA says that while the comet is heading in that direction, it will never approach more than 1 billion miles away from the Sun, or a little further away from Earth and Saturn. It will also not reach this closest point on Earth until 2031. How comet C / 2014 UN271 (Bernardinelli-Bernstein) nucleus was isolated from a huge shell of dust and gas surrounding the solid frozen nucleus. To the left is a photograph of the comet taken by NASA’s Hubble Space Telescope Wide Field 3 camera on January 8, 2022. A model of the coma (middle frame) was obtained by adjusting the brightness profile of the surface assembled from the observed image in left. This allowed the coma to be removed, revealing the sharp glow from the nucleus. Combined with radio telescope data, astronomers have come up with an accurate measurement of the size of the nucleus. This is no small feat from about 2 billion miles away. Although the core is estimated to be as large as 85 miles, it is so far that it cannot be solved by Hubble. Its size is determined by its reflectivity as measured by Hubble. The core is estimated to be black as coal. The core area is collected by radio observations.
The largest comet ever observed
At about 80 miles wide, it is better than the previous record C / 2022 VQ94 discovered in 2022 by Lincoln Near-Earth Asteroid Research (LINEAR) and had a core about 60 miles wide. For reference, Comet Neowise is only about three miles in diameter and Halley Comet is seven miles in diameter. 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 Observatory in Chile. The comet was first observed in November 2010, when it was three billion miles from the Sun, or about the average distance of Poseidon from Earth. Since then, astronomers have been studying it from both ground and space telescopes. While observed a decade ago, its true size could not be confirmed until very recently. Credits: Illustration: NASA, ESA, Zena Levy (STScI) The diagram above compares the size of the frozen, solid core of comet C / 2014 UN271 (Bernardinelli-Bernstein) with several other comets. NASA says the majority of comet nuclei observed are smaller than the Halley comet and are usually a mile or less. “This is an amazing object, given how active it is when it is still so far from the Sun,” said Man-To Hui, lead author of the work at Macau University of Science and Technology, Taipa, Macau. “We guessed the comet might be big enough, but we needed the best data to confirm it.”
Separation of the Nucleus from the Coma
NASA says determining the true size of a comet can be difficult because it is often difficult to distinguish the core of an object from the huge dusty coma that surrounds it. At present, only the Hubble Space Telescope has the sharpness and sensitivity to make a definitive estimate of the size of the core, but it is still too far to be resolved by Hubble’s cameras alone. Hui and his team used Hubble to capture five images of the comet on January 8, 2022. The historic space telescope was able to show a bright beam of light in the center of what it could see, indicating the location of the nucleus. They then made a computer model of the coma environment and adapted it to fit the new Hubble images. They then removed it from the Hubble images to get a photo of the core. The team compared this result with the luminosity of the nucleus observed by the Atacama Large Millimeter / submillimeter Array (ALMA) array in Chile, in order to achieve a more accurate measurement of its diameter as well as its reflectivity. What they found is that the comet’s size is close to what was previously estimated by ALMA, but that it is also a very dark comment – much darker than previously thought. Not only is it large, but it is also blacker than coal. “This comet is literally the tip of the iceberg for many thousands of comets that are too dim to see in the most remote 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, he says. “We always suspected that this comet had to be big because it is so bright at such a distance. “Now we confirm that it is.”
An elliptical orbit of three million years
NASA says the Bernardinelli-Bernstein comet has been moving toward the Sun for more than a million years and is thought to come from a “nested ground” of trillions of comets called the Oort Cloud. The comet follows an elliptical orbit of three million years that takes it away from the Sun for about half a year of light. It is now less than two billion miles from the sun and falls almost perpendicular to the level of the Earth’s solar system. At such a distance, the temperature around the comet is a cold minus 348 degrees Fahrenheit, which is hot enough for carbon monoxide to sublimate from the surface to form the dusty coma that surrounds it. Image Credits: Images from NASA, ESA, Man-To Hui (Macau University of Science and Technology), David Jewitt (UCLA). Image Editing: Alyssa Pagan (STScI)
