Turns Out the Megacomet Is More Than 80 Miles Wide—and It's Headed Our Way

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Last year, the monstrous Bernardinelli-Bernstein comet (also known as C/2014 UN271) was discovered by the eponymous University of Pennsylvania astronomers Gary Bernstein and Pedro Bernardinelli. The pair called it the “nearly spherical cow of comets” in their paper about the discovery, but it wasn’t long until the world dubbed it the “megacomet” for being an absolute unit of a space object.

While the megacomet fell out of the main space news spotlight, NASA astronomers set the the Hubble Space Telescope’s sights on the object in the months since—and discovered how truly immense it is. A new paper published in The Astrophysical Journal Letters on Tuesday confirmed that Bernardinelli-Bernstein had a nucleus—the icy core at the center of all comets—that’s more than 80 miles wide. That’s roughly 50 times larger than other comets and the largest ever observed.

“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,” David Jewitt, a professor of planetary science and astronomy at the UCLA and co-author of the study, said in a NASA press release. “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.”

Even with the imagery provided by the Hubble, scientists still had their work cut out for them in sussing out its precise size. After all, the megacomet is still incredibly far away. So the team had to process images taken of the comet by the Hubble in a computer model, which gave them an approximate estimation of its mass. Now astronomers can confirm that the Bernardinelli-Bernstein comet is much larger than any other comet ever discovered. The previous record was held by C/2002 VQ94, which had a nucleus that’s a mere 60 miles across.

<div class="inline-image__caption"><p>A size comparison of the Benardinelli-Bernstein comet's nucleus to other notable comets. </p></div> <div class="inline-image__credit">NASA, ESA, Zena Levy (STScI)</div>

A size comparison of the Benardinelli-Bernstein comet's nucleus to other notable comets.

NASA, ESA, Zena Levy (STScI)

Disconcertingly, the megacomet is on an interstellar road trip that’ll bring it right through our solar system in 2031. Luckily for us, it’s not expected to get any closer than a billion miles away from the sun, passing between Saturn and Uranus’ respective orbits. This won’t be the first time it’s made such a trip either since most comets observed originated from the collision of space rocks that created Earth long ago. In fact, the megacomet is following a 3-million-year-long elliptical orbit—so it’s been a minute since we’ve seen it last.

Its next approach in nine years will provide astronomers with a very rare opportunity to closely study an object that might still contain remnants from the early solar system. With the mighty James Webb Space Telescope unfurled and in orbit, there’s a chance we could get an even more in-depth look at the comet than we ever have before.

“It’s pristine,” Bernardinelli told The Daily Beast last year. “Not a lot has happened to this object since its formation in the early days of the solar system, and so we can think of it as a window into the past.”

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