Hubble Confirms Inner Solar System-Bound Megacomet Is Largest Ever Seen

A gigantic comet is in fact the largest ever seen, as confirmed by new observations from the Hubble Space Telescope.

Stretching about 80 miles (129 kilometers) in diameter, the core (or solid center) of the comet, known as C/2014 UN271 (Bernardinelli-Bernstein), is larger than the state of Rhode Island, according to a NASA statement. And it’s about 50 times larger than the average nucleus of a comet.

“This comet is literally the tip of the iceberg for several thousand comets that are too faint to be seen in the most distant parts of the solar system,” said David Jewitt, co-author of a new study confirming the size. of the comet and professor of planetary sciences and astronomy at the University of California, Los Angeles (UCLA), says in NASA statement. “We always suspected that this comet must be big because it is so bright at such a great distance. Now we confirm that it is.

This comet is currently far from Earth, speeding at around 22,000 mph (35,405 km/h). Comet Bernardinelli-Bernstein has been falling toward the sun for over a million years. But do not worry ; the closest to us, according to NASA, is about 1 billion miles (1.6 billion km), which it won’t even reach until 2031.

Previously, the comet that held the title of “largest nucleus” was C/2002 VQ94, which was spotted in 2002 and estimated to be about 60 miles (96 km) in diameter.

This new behemoth of a comet was first observed in 2010. A few years later, astronomers Pedro Bernardineli and Gary Bernstein found the object in archival data collected by the Dark Energy Survey at the Observatory. Inter-American Cerro Tololo in Chile. Since its original discovery, the object has been studied using a wide range of instruments, including ground-based telescopes and space-based telescopes like Hubble.

Thanks to Hubble observations, the researchers were finally able to officially confirm the gigantic size of this “dirty snowball”. (Comets are nicknamed “dirty snowballs” because they are made of rock, ice, and other materials and debris, although the objects can vary in composition.) At this point in Comet Bernardinelli’s orbit- Bernstein, in which it is “only” 2 billion miles (3.2 billion km) from the sun, the icy object is about minus 348 degrees Fahrenheit (minus 211 degrees Celsius).

Although freezing, this temperature is warm enough to allow carbon monoxide to sublimate (a process in which solid material becomes a gas) from the rocky surface of the comet, creating a “coma”, an envelope of dust and gas that surrounds the solid center of a comet.

“It’s an amazing object, considering how active it is when it’s still so far from the sun,” said study lead author Man-To Hui, a researcher at the University of Science and Technology. of Macau, in the same NASA statement. “We guessed the comet might be quite large, but we needed the best data to confirm that.” So his team used Hubble to take five photos of the comet on January 8, 2022.

The team’s main challenge in confirming the size of the nucleus was to tell the difference between the nucleus and the comet’s coma.

Bernardinelli-Bernstein is too far away for Hubble to define its nucleus exactly, but the team detected a bright signal with the telescope, indicating the location of the comet. They were then able to use the Hubble observations they had and, using a computer modeling technique to show where the object’s coma would be, they were able to determine the size of its core.

The team compared their data with earlier observations made by the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile and found that earlier size estimates made with ALMA aligned with the new findings from Hubble. And ALMA’s radio observations allowed them to focus on the object’s reflectivity, showing that the comet’s surface is darker than expected.

“It’s big, and it’s blacker than coal,” Jewitt said.

Scientists believe comet Bernardinelli-Bernstein is traveling from Oort Cloud, the outermost region of our solar system where a large number of comets reside. The comets in this huge diffuse cloud are thought to have formed closer to the sun but were thrown much farther by gravitational interactions with the fledgling giant planets of our solar system. And they tend to stay there unless another gravitational pull pushes them towards us.

This comet, being so distant from Earth and originating in the farthest reaches of our solar system, is believed to travel over a period of 3 million years. elliptical orbit around the Sun. Scientists believe it could travel about half a light-year from the sun in the farthest parts of its orbit.

These findings were described in a study published today (April 12) in The Astrophysical Journal Letters.

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