Comet Returns for First Time Since the Stone Age

A comet that hasn't visited our part of the solar system since the Stone Age will be closest to Earth in mid-October and people should "savor the view," says NASA astronomer Bill Cooke. Comet C/2023 A3 Tsuchinshan–ATLAS hasn't been visible from Earth since 80,000 years ago, when Neanderthals would have been among the stargazers, the Guardian reports. It was spotted by astronomers last year and was named after the two observatories, one in China and one in South Africa, that detected it. Gregory Brown, senior public astronomy officer at the Royal Observatory Greenwich, says it "is already visible to the unaided eye in good conditions, and there is a chance that it will get considerably brighter."

Astronomers believe the comet originated in the Oort cloud at the edge of the solar system. It wasn't clear whether it would survive its closest transit past the sun on Sept. 27, "but it survived more or less intact," NASA says. It will be closest to Earth, at around 44 million miles away, on Oct. 12, though since it will be directly between the sun and the Earth at the time, the best viewing window will be the days on either side of that date, Brown says. "Naked-eye-visible comets are rare enough as it is, and this one has the potential to be amongst the brightest that we've seen in the last few decades," he tells the Guardian. "So it's certainly worth a go." He says the comet may be at its brightest on Oct. 9.

People in the southern hemisphere will have the best view, but it will also be visible from the northern hemisphere. Cooke, chief of the Meteoroid Environment Office at NASA's Marshall Space Flight Center, suggests finding a dark vantage point just after full nightfall. He says brightness is hard to predict with comets, but it could be "truly spectacular with binoculars or a small telescope." More viewing tips from NASA: "Looking to the southwest, roughly 10 degrees above the horizon, identify the constellations of Sagittarius and Scorpio. Tsuchinshan-ATLAS should be visible between them. By Oct. 14, the comet may remain visible at the midway point between the bright star Arcturus and the planet Venus." (More comet stories.)