Comet C/2014 UN271 (Bernardinelli-Bernstein) is the next big thing in astronomy news. This behemoth spans 80 miles across and weighs approximately 500 trillion tons, making it the most enormous known comet in existence.
Astronomers Pedro Bernardinelli and Gary Bernstein first discovered C/2014 UN271 in November 2010 at the Cerro Tololo Inter-American Observatory in Chile. Despite being studied intensely by both grounded and space-based telescopes, C/2014 UN271’s approximate remained a mystery until now.
How Did NASA Approximate Comet C/2014 UN271’s Size?
Since the discovery of Bernardinelli-Bernstein was over a decade ago, the time it took to approximate its size is curious. However, the story of resolving its size is the most intriguing part of its story, serving as an informative lesson for aspiring astronomers on deductive math and reasoning.
The key to NASA’s process was the Hubble Space telescope, although it alone was not strong enough to measure the comet’s dimensions from billions of miles away. In addition, because the comet traveled over a billion miles closer to NASA’s instrument in the 12 years since its discovery, the passage of time gave NASA a much better view of its nucleus.
These factors were indispensable for the team, including the research paper’s head author, Man-To Hui of the Macau University of Science and Technology, Taipa, Macau.
“This is an amazing object, given how active it is when it’s still so far from the Sun,” said Man-To Hui in an interview with NASA. “We guessed the comet might be pretty big, but we needed the best data to confirm this.”
First, Hubble took five images of the comet, which were then compared to those taken in 2010 by Chile’s Atacama Large Millimeter/submillimeter Array (ALMA) telescope. The Hubble images suggested similar measurements but unveiled a darker and much bigger nucleus than ALMA’s rendition.
The obstacle here was separating the comet’s nucleus from its massive “coma” or “tail,” which is melting ice and dust particles departing from the nucleus as it gets closer to the sun. To do this, Hui’s team made a computer model of the coma and fit it according to Hubble’s images.
Next, they detracted the coma from the model, which gave them an approximate size of the nucleus fit to the photos. With only the core remaining in their imagery, they could approximate its size.
No, Earth Is Not in Danger of a Collision
NASA’s discovery of Comet Bernardinelli-Bernstein’s size has prompted countless clickbait opportunities. Appropriating the theme of Netflix’s film “Don’t Look Up,” Publications have released headlines suggesting the possibility of Comet Bernardinelli-Bernstein colliding with Earth. This couldn’t be farther from the truth. 1-billion miles farther, in fact.
Astronomers have long been subject to spin for the media’s benefit. For example, in 2020, headlines warned of an asteroid coming for Earth on election day, creating a field day out of American Astrophysicist Neil Degrasse Tyson’s words. In actuality, Tyson examined this interesting phenomenon while making a joke about American politics.
“Asteroid 2018VP1, a refrigerator-sized space-rock, is hurtling towards us at more than 40,000 km/hr. It may buzz-cut Earth on Nov 2, the day before the Presidential Election. It’s not big enough to cause harm. So if the World ends in 2020, it won’t be the fault of the Universe,” Tyson’s tweet read.
Comet Bernardinelli-Bernstein orbits the sun along a 3-million-year-long elliptical orbit, reaching as far as half a light-year away from the sun before starting its return. At the closest point of orbit, it will still be about 1 billion miles away from the sun. For context, at this distance, temperatures remain negative 348 degrees Fahrenheit.
A Comet’s Journey
Like all comets, Bernardinelli-Bernstein is thought to originate in the “Home of Comets” called the Oort Cloud. The Oort Cloud is theorized to be a sphere of icy debris surrounding our entire solar system like a bubble. When pieces of ice dislodge from this bubble, they get trapped in the sun’s gravitational pull and thus become comets.
Anecdotal evidence can trace other known comets back to this region in the farthest reaches of our solar system. However, it is still considered a theory because it is too far away to map accurately. Nevertheless, Berardinelli-Bernstein offers astronomers an idea of the relative size of other icy bodies, opening the imagination to possibly more giant comets.
Co-author of NASA’s study on Bernardinelli-Bernstein David Jewitt shared his excitement for future discoveries in an interview with NASA.
“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 Jewitt. “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.”
At 60 miles long, the previous largest comet known was C/2002 VQ94, discovered in 2002 by the Lincoln Near-Earth Asteroid Research (LINEAR) project. So who knows what will fall out of the Oort Cloud next?
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