Did You Miss The ‘Green Comet?’ A New Naked-Eye Comet Just Spotted Could Get Brighter Than Venus
Comet C/2022 E3 was visible in February 2022.
Did you see the “green comet” last month? February’s icy visitor was a little tricky to find with the naked eye, but that may not be the case with a much brighter “new” comet just spotted by astronomers.
Called C/2023 A3 (Tsuchinshan-ATLAS) and discovered simultaneously by telescopes in both Africa and China, little is known about this comet aside from its orbit, which will bring it closest to earth in October 2024.
How bright will the comet become?
It could be worth the wait because comet C/2023 A3 may just reach a brightness similar to that of the planet Venus. That’s incredibly bright—and way brighter than either February’s C/2023 E3 or Comet NEOWISE in summer 2020.
Currently over seven Earth-Sun distances away from us—so roughly between Mars and Jupiter—comet C/2023 A3 will get closest to the Sun on September 28, 2024 (inside the orbit of Mercury, in fact—hence the high brightness predictions) and pass closest to Earth on October 12, 2024.
When will the comet be brightest?
Something called forward-scattering could cause comet C/2023 A3 to reach -5 magnitude during mid-October as it becomes visible in the northern hemisphere’s western sky. However, the angle of comet C/2023 A3’s entry and exit from the solar system means it will pass between Earth and the Sun, which means it will only be visible close to sunrise and sunset in late September and mid-October 2024.
Comet-watchers in the northern hemisphere may have the wait until later in October 2024 when the comet leaves the Sun’s glare and becomes visible after sunset—and relatively close to Venus by eye.
Why visible comets are difficult to predict
It’s also true that the future brightness of comets is notoriously difficult to predict. After all, comet C/2023 A3 is very distant and difficult to observe. To be bright it will first need to survive getting close to the Sun, but will also require a large nucleus and a dusty tail—something that is currently impossible to judge.
With those caveats in hand, comet C/2023 A3 could be a truly incredible sight. So why not make a plan to be in or near an International Dark Sky Place in mid-to-late October 2024 so you can get the best post-sunset views, just in case?
This comet is also a ‘Stone Age’ comet
Although a lot of fuss was made about comet C/2023 E3 having an orbit of 55,000 years—a scientifically unremarkable fact that nevertheless earned it the nickname the “Neanderthal comet” and “Stone Age comet”—comet C/2023 A3 is reckoned to have an orbit of just over 80,000 years.
Where does the comet come from?
Long-period comets like C/2023 A3 and C/2023 E3 hang out in the Oort Cloud, a sphere around our solar system that’s around 100,000 times the Earth-Sun distance miles from us.
How did this comet get its name?
C/2023 A3 (Tsuchinshan-ATLAS)’s name comes from the fact that it was discovered on February 22, 2023 by astronomers at both China’s Tsuchinshan Observatory and South Africa’s Asteroid Terrestrial-impact Last Alert System (ATLAS) telescope.
Wishing you clear skies and wide eyes.
