A comet that hasn’t been seen from Earth since Neanderthals were alive and kicking has reappeared in the sky, with astronomers saying it might be visible to the naked eye.
Comet C/2023 A3 (Tsuchinshan–Atlas) was discovered by astronomers early last year and is thought to orbit the sun on a highly elongated path every 80,000 years.
Dr Gregory Brown, the senior public astronomy officer at the Royal Observatory Greenwich, said the comet was thought to have originated in the Oort Cloud, which lies beyond Neptune’s orbit.
“[This is] the vast, more or less spherical region around the sun, which has icy remnants from the formation of the solar system,” he said.
But now the comet is in our neck of the woods. After making its closest approach to the sun at the end of last month, it is expected to do the same to Earth around October 13.
“The thing about comets is that the closer they are to us, to Earth, the brighter they are, but also the closer they are to the sun, the brighter they are. So the closest approach is not necessarily going to be the clearest time,” Brown said, noting that it could fall around October 9 instead.
At that point, however, the comet will be almost directly between the Earth and the sun. As a result, Brown said, the best time to look for it would be a few days before and after.
“Comets visible to the naked eye are rare enough as they are, and this one has the potential to be one of the brightest we’ve seen in decades. So it’s definitely worth going,” he said.
Brown said it’s hard to be sure how bright the comet will get as it gets closer.
“By preventing it, it is already visible to the naked eye in good conditions, and there is a chance that it will become significantly brighter,” he said. “But how bright? We honestly don’t know.”
Brown said stargazers in the northern and southern hemispheres have a chance to see the comet.
Currently, he added, viewers should look east in the early morning before sunrise, toward the constellation Sextans.
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But he said, “It’s going to swing on the other side of the sun over the next few days.”
As a result, Brown said as of October 13, the best chance to see the comet is late evening, after sunset, looking west toward the constellation Boötes.
Brown said the comet would likely appear as a speck in the sky to the naked eye — although its tail should be visible with binoculars or a small telescope.
Even if the display is not as spectacular as experts hope, stargazers can enjoy the knowledge that they are among the first to lay eyes on the comet since the Stone Age.
“And of course there’s no way of knowing how bright the comet would have been and how easy it would have been to see,” Brown said.
