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Comet Bernardinelli-Bernstein, the largest comet in history, was discovered by Pedro Bernardinelli who received his Ph.D. in astrophysics from Penn in 2021 and professor of Astronomy and Astrophysics Gary Bernstein. (Photo from Department of Physics and Astronomy)

Two Penn astronomers discovered the largest comet in history which will reach its closest point to Earth in 2031, according to data from the Dark Energy Survey.

Comet Bernardinelli-Bernstein was named on June 24 after Pedro Bernardinelli, who received his Ph.D. in astrophysics from Penn in 2021, and professor of Astronomy and Astrophysics Gary Bernstein — the two astronomers who discovered it. The comet — officially termed "C/2014 UN271" — is estimated to be between 62 and 125 miles long, making it 10 times the diameter of many comets and larger than the island of Hawaii, The New York Times reported.

Bernardinelli and Bernstein discovered the comet by analyzing archival images from the 2014 DES Project, which mapped out 300 million galaxies from billions of light years away over the course of six years. During the project, the imaging also detected many comets that passed by and objects floating around the planet Neptune, including the record-breaking Comet Bernardinelli-Bernstein.

When Comet Bernardinelli-Bernstein was originally detected in 2014, it was over two billion miles away. The comet is now 1.8 billion miles away, making it the largest comet on an incoming path to be detected from so far away, according to Noir Lab. Its far distance will allow astronomers to train their telescopes on the comet and watch its behavior for the next 20 years.

In 2031, the comet will reach its closest point to Earth, just outside of Saturn's orbit, according to The New York Times. Since it will still be about a billion miles away when it approaches Earth in 2031, it will not show a visible streak like most comets but rather a flicker. Skywatchers will likely have to use a strong telescope to observe it, Bernstein told Penn Today, adding that comets' behaviors are generally hard to predict.

“Comets are like cats. You never know what they’re going to do," Meg Schwamb, an astronomer at Queen’s University Belfast, told The New York Times. “I’m ready to get the popcorn.”

Scientists estimate that the comet originated from the Oort Cloud, a shell of space debris on the outskirts of our solar system, according to NASA. They predict that there could be more giant comets that will be discovered from this region after the migration of the gas giants in their early history.

“We have the privilege of having discovered perhaps the largest comet ever seen, or at least bigger than any well-studied one, and caught it early enough for people to watch it evolve as it approaches and warms up,” Bernstein told Penn Today.

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