A mega-comet lurks in our solar system, spewing carbon monoxide • The Register


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Not only is comet Bernardinelli-Bernstein the largest of its kind known, but it’s also one of the most active and distant comets, likely spewing plumes of gas farther from the Sun than expected.

The object, code name C / 2014 UN271 (Bernardinelli-Bernstein) or simply comet BB, was first spotted in 2014. It was provisionally considered a minor planet, which means that it could be an asteroid, a transneptunian object or even a dwarf planet. After researchers working at the Las Cumbres Observatory in California discovered a coma – a hazy halo of gas enveloping the object, which is typically found around comets – it was referred to as a comet.

Measuring 100 km in diameter, comet BB is about 1,000 times the size of the average icy space rock we observe, and has made headlines for being the largest such object known to science.

Digital render of comet BB … Image credit: NOIRLab / NSF / AURA / J. da Silva / spacecraft

It orbits the Sun at a distance beyond Uranus, and its coma has revealed that it is also one of the most active comets. Most comets are inert and push molecules from their surface and form tails of gas and dust when they are close enough to the Sun to be warmed by the star’s rays. The molecules are usually formed from the ice evaporating from its nucleus. Active comets are therefore normally found closer to our star.

Now a study published this week in The Planetary Science Journal suggests that the mega-comet entered a coma at a surprising 23.8 astronomical units (AU) from the Sun – roughly 24 times the distance between Earth and our star, or more than 2.2 billion miles.

Scientists believe he was likely active not only at this enormous distance, breathing out gases and possibly other material, but also at distances greater than those previously measured, which is important.

The point at which a comet is activated by the Sun reveals clues to the composition of the rock, as different chemicals activate at certain distances. Not only that, it is unheard of so far for a rock this big to be active this far.

“These observations push the distances of active comets considerably farther than we previously thought,” Tony Farnham, senior author of the article and researcher in the Department of Astronomy at the University of Maryland, noted in a report.

“We’re assuming comet BB was probably active even further away, but we just haven’t seen it before that. What we don’t know yet is if there is an endpoint where we can start. see these things in a cold store before they become active.

Farnham explained to The register that comet BB is most likely ejecting carbon monoxide molecules.

CO begins to activate first, at very great distances, so we suspect that it is the gas that drives the activity we see in this comet.

“The three main components that produce activity in comets are carbon monoxide (CO), carbon dioxide (CO2) and water. CO begins to activate first, at very great distances, so we suspect that it is the gas that drives the activity we see in this comet. CO2 needs hotter temperatures to evaporate and activates around 10-12 AU, and the water needs the hottest, activating around 3 AU.

“We should be able to track CO and CO2 activity to confirm that they initiated the activity. Unfortunately, the comet reaches perihelion at about 10 AU, around Saturn’s orbit, so water will never be a big contributor, and it will never get very bright, even if the nucleus is large.

The perihelion being the closest point at which an object orbiting the Sun is closest to the star.

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Farnham believes comet BB could help astronomers understand how comets and the solar system form: “We have little data on the start-up processes of how comets become active, and find them at heliocentric distances of larger and larger helps provide data on these processes. Do they “turn on” and become continuously active or do they start and stop for a while before fully turning on? “

“The large nucleus also allows us to address questions about comet formation, which ultimately leads to information about the formation of the solar system. These large objects are unusual and can fill gaps in our understanding of how bodies accumulate to produce comets, asteroids and ultimately planets, ”he concluded. ®

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Arline J. Mercier