PORTLAND, Maine — A comet barely visible in Maine’s pre-dawn skies this weekend may become the brightest thing in the heavens, other than the moon, by the middle of next month.
Or maybe not. It’s hard to tell for sure. Here’s why.
Any comet’s visual brilliance is notoriously hard to predict in advance — and it’s even more difficult with this one, since we’ve never seen it pass through our solar system before.
But many sky-watching optimists are hoping C/2023 A3, better known as Tsuchinshan-ATLAS, turns out to be the “comet of the century,” even outshining the spectacular NEOWISE, which passed this way in July 2020.
Astronomers at the Purple Mountain Observatory in China first spotted Tsuchinshan-ATLAS in January 2023. However, scientists lost sight of the faint, distant speck of light just a few weeks later. Then, in February that year, NASA’s Asteroid Terrestrial-Impact Last Alert System of telescopes, scanning the sky for unknown objects, caught sight of Tsuchinshan-ATLAS again.
Now, it’s finally reached our planetary neighborhood. On Friday, Sept. 27, Tsuchinshan-ATLAS reached its closest point to the sun and is now making its way directly around our star.
“Since its initial discovery, amateur astronomers and scientists around the world have made thousands more observations of this comet,” said Asa Stahl, a California-based astrophysicist, and award-winning children’s book author. “Many are tracking Tsuchinshan-ATLAS in hopes that it will become extremely bright — so bright that it outshines the stars, Jupiter, and even Venus.”
Like all comets, this one is basically a giant, space-traveling dirty snowball of ice and organic materials leftover after the formation of our solar system around 4.6 billion years ago. Its tail is made of dust and vaporizing gasses given off as it passes close to the sun.
What we see when we look up at night is sunlight reflecting off that tail, and therein lies the rub.
So far Comet Tsuchinshan-ATLAS looks like a fuzzy star to the naked eye looking out the cupola windows. But with a 200mm, f2 lens at 1/8s exposure you can really start to see it. This comet is going to make for some really cool images as it gets closer to the sun. For now a… pic.twitter.com/JstaSLJ4Ui
— Matthew Dominick (@dominickmatthew) September 19, 2024
A comet’s reflected light scatters at a shallow angle and we’ve got to be in just the right position to see its brilliance. Also, no two comets are alike in composition, some are made of more volatile gasses than others. What’s more, astronomers believe Tsuchinshan-Atlas has probably never been around the sun before and could actually break apart and fizzle out during the process.
But precisely because it’s a solar system newbie, it also might be spectacular, burning off a huge amount of gas and dust on its first trip around the sun. The only way to know for sure is to wait and see.
“Already, Comet Tsuchinshan-ATLAS has gotten about one million times brighter over the past couple years as it has traveled closer to the sun,” Stahl said.
To see it right now, you’ll need to get up early, about an hour before dawn, and find a good view of the eastern horizon as far away from city lights as you can get. A pair of light-gathering binoculars will help in a big way.
Look at the mostly unknown constellation Sextans, which lies between the better known formations of Leo to the north and Hydra to the southwest. If it’s clear you’ll be able to spot Tsuchinshan-ATLAS. It will only look like a faint smudge.
But things could be a lot different by the middle of next month. By Oct. 10, Tsuchinshan-ATLAS will be passing close to Earth and, if everything goes well, it could be spectacular.
At that time, you won’t even have to get up early to see it.
Instead look above the western horizon about an hour after sunset. By then, Tsuchinshan-ATLAS will be speeding through the constellations Leo and Virgo. If it’s putting on a show, even Mainers in light-polluted cities should be able to spot it.
Whether it turns out to be an amazing sight or celestial dud, this is our only chance to see Tsuchinshan-ATLAS. Judging by the shape of its orbit, scientists believe the comet won’t be back this way for several hundred-thousand years — and there’s also a good chance it’ll be ejected from the solar system altogether and just keep on hurtling out into the void, never to return.
