One Of The Largest Comets Ever Seen Is Headed Our Way

“My phone didn’t stop ringing—I wasn’t expecting the reception the [scientific] community gave to the discovery,” says Pedro Bernardinelli, a postdoctoral researcher at the University of Washington. He co-discovered the comet during the final weeks of his Ph.D. research at the University of Pennsylvania with his then-adviser Gary Bernstein. “Overall, it’s been pretty overwhelming.”

The latest estimates put the comet’s nucleus at about 93 miles (150 kilometers) wide. That’s by far the biggest size estimate for a comet in decades. By contrast, comet 67P/Churyumov–Gerasimenko, which the European Space Agency’s Rosetta spacecraft orbited from 2014 to 2016, was only about 2.5 miles wide.

“We’re going from your city-size comets to your island-size comets,” says Michele Bannister, an astronomer at New Zealand’s University of Canterbury who was not involved in the discovery paper. Comet Bernardinelli-Bernstein’s size may even rank alongside some historical “great comets,” including a very bright—and presumably huge—comet that journeyed into the inner solar system in 1729.

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Over the next decade, Bernardinelli-Bernstein will continue to get brighter as it approaches the inner solar system, dive-bombing the plane of the planets’ orbits from below. It will make its closest approach on January 21, 2031, when the comet is expected to come within about a billion miles of the sun, slightly farther away than Saturn’s average distance. It will then begin its long retreat back into the solar system’s outer realms, remaining visible into at least the 2040s, if not decades longer.

Depending on how much gas the comet releases as its ices vaporize in the sun’s glare, Bernardinelli-Bernstein could get as bright in the night sky as Saturn’s largest moon Titan. If so, the comet should be visible in 2031 with a decent backyard telescope.