Hubble Space Telescope Confirms Largest Comet Nucleus Ever Seen

NASA’s Hubble Space Telescope has confirmed the existence of a comet nucleus that’s larger than the State of Rhode Island and has a mass of more than 500 trillion tons.

Even though the James Webb telescope is coming online this year—the space telescope’s first image of a star is incredible—NASA’s Hubble space telescope is still churning out impressive pics of its own. In a new stunner, Hubble has captured an image that confirms the existence of the largest comet nucleus ever observed; one that’s 80 miles across and 500 trillion tons in mass.

Image: NOIRLab/NSF/Aura/J. da Silva (spaceengine)

NASA put out a press release on the jumbo comet nucleus, which is “barreling this way at 22,000 miles per hour from the edge of the solar system.” The space agency notes that folks don’t need to worry, however, as the comet nucleus—dubbed C/2014 UN271 (Bernardinelli-Bernstein)—will never get closer than 1 billion miles away from the Sun; a distance that is longer than that between Earth and Saturn.

“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). Jewitt, a co-author of a new study in The Astrophysical Journal Letters outlining the findings from the Hubble comet-nucleus image, added that “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.”

NASA reports that C/2014 UN271‘s nucleus is about 50 times larger than those found at the hearts of most comets that have been observed. Astronomers estimate its mass at a staggering 500 trillion tons—100,000 times greater than the mass of a typical comet found in proximity to the Sun.

“This is an amazing object, given how active it is when it’s still so far from the Sun,” said the study’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.” To obtain that data, he and his team used Hubble to snap five pictures of the comet on January 8, 2022.

Image: NASA, ESA, Zena Levy (STScI)

NASA notes the biggest challenge for the astronomers was figuring out how to discriminate the solid nucleus from the huge dusty coma—or bright outflowing atmosphere—enveloping it. The comet is too far away for its nucleus to be visually resolved by Hubble, which meant Hui et al. had to rely on Hubble data showing “a bright spike of light at the nucleus’ location.” Hui and his team then made a computer model of the surrounding coma and adjusted it to fit the Hubble images. The coma’s glow was subsequently subtracted, leaving behind the “starlike” nucleus.

The comet has apparently been hurtling toward our home star for more than a million years. Astronomers believe its origin was amongst the “nesting ground of trillions of comets” referred to as the Oort Cloud; a diffuse cloud of predominantly icy planetesimals that’s believed to have an inner edge that’s somewhere between 2,000 to 5,000 times the distance between the Sun and Earth. NASA notes the outer edge of the cloud, which encircles our solar system, may extend at least a quarter of the way out of the distance to the Alpha Centauri system.

Image: NASA, ESA, Man-To Hui (Macau University of Science and Technology), David Jewitt (UCLA); Alyssa Pagan (STScI)

Incredibly, Hui and his team found the new Hubble images suggest a darker nucleus surface than previously thought. Jewitt added in the press release that the comet nucleus is “big and… blacker than coal.” A slightly ominous observation, as it brings to mind all of the giant comet nuclei out there not lit up by the Sun.

Feature image: NASA Goddard

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