A 4 billion-year-old remnant from the early solar system is on its way to Earth.

A massive comet, some 80 miles in diameter and more than twice the breadth of Rhode Island, is speeding towards us from the boundary of the solar system at 22,000 miles per hour. Fortunately, it will never approach closer to the sun than 1 billion miles, which is somewhat closer to Earth than Saturn; the closest it will get is in 2031.

According to David Jewitt, comets, which are among the earliest things in the solar system, are frozen bodies that were rudely thrown out of the solar system in a gravitational pinball game between the giant outer planets. The UCLA planetary science and astronomy professor co-authored a new analysis of the comet in the Astrophysical Journal Letters. The ejected comets settled in the Oort cloud, a large reservoir of far-flung comets that encircles the solar system and extends billions of miles into deep space, he said.

A typical comet’s magnificent multimillion-mile-long tail, which makes it appear like a skyrocket, conceals the reality that the source of the fireworks is a solid nucleus of ice mixed with dust—basically a dirty snowball. Comet C/2014 UN271, discovered by astronomers Pedro Bernardinelli and Gary Bernstein, could be as enormous as 85 miles across.

“This comet is essentially the tip of the iceberg for many thousands of comets that are too faint to view in the more distant portions of the solar system,” Jewitt added. We’ve always assumed that this comet had to be massive because it’s so bright at such a great distance. We now have confirmation. “

This comet has the biggest nucleus ever observed in a comet by astronomers. Using NASA’s Hubble Space Telescope, Jewitt and his colleagues calculated the size of the nucleus. Its nucleus is around 50 times larger than that of most known comets. Its mass is predicted to be 500 trillion tons, which is a hundred thousand times bigger than the mass of a typical comet found much closer to the sun.

“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, 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.”

Jewitt said.

“This is an astonishing item, given how active it is when it’s still so far from the sun,” said lead author Man-To Hui, who obtained his doctorate from UCLA in 2019 and is now with the Macau University of Science and Technology in Taipa, Macau. “We believed the comet might be quite large, but we required the best data to confirm this.”

So, on Jan. 8, 2022, the researchers utilized Hubble to acquire five images of the comet and added radio observations of the comet to their study.

According to Jewitt, the comet is now fewer than 2 billion miles from the sun and will loop back to its nesting area in the Oort cloud in a few million years.

Comet C/2014 UN271 was discovered by chance in 2010, when it was 3 billion miles from the sun. It has been extensively investigated since then by land-based and space-based telescopes.

The difficulty in measuring this comet was determining the solid nucleus from the massive dusty coma—the cloud of dust and gas that enveloped it. Hubble can’t see the nucleus of the comet right now because it’s too far away. The Hubble data, on the other hand, shows a sharp spike of light at the nucleus’ location. Hui and his colleagues then created a computer model of the surrounding coma, which they tweaked to fit the Hubble photos. They then removed the coma’s luminescence, leaving only the nucleus.

Hui and his colleagues compared the brightness of the nucleus to previous radio measurements from Chile’s Atacama Large Millimeter/submillimeter Array, or ALMA. The latest Hubble observations are similar to prior ALMA size estimates, but they strongly suggest a darker nucleus surface than previously anticipated.

“It’s huge, and it’s blacker than coal,” Jewitt remarked.

For nearly a million years, the comet has been heading toward the sun. The Oort cloud is supposed to be a breeding environment for billions of comets. Jewitt believes the Oort cloud stretches from a few hundred times the distance between the sun and the Earth to at least a fourth of the way out to the distance of the nearest stars to our solar system in the Alpha Centauri system.

According to Jewitt, the enormous outer planets’ gravitational pull threw the comets of the Oort cloud out of the solar system billions of years ago. According to the professor, far-flung comets return to the sun and planets only if their orbits are interrupted by the gravitational push of a passing star.

The Oort cloud, first proposed by Dutch astronomer Jan Oort in 1950, is still a theory because the comets that make it up are too faint and distant to be directly viewed. According to Jewitt, this suggests that the solar system’s biggest structure is nearly invisible.

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