When is the next comet? If you glimpsed comet 2022 E3 (ZTF)—the so-called “green comet” —and 2020’s comet NEOWISE then you may be wondering when the next icy snowball is going to be visible from Earth.
Comets that are visible to the naked eye are notoriously difficult to predict in advance, but that doesn’t stop astronomers from trying. The latest comet to pique the interest of astronomers is comet C/2023 A3 (Tsuchinshan-ATLAS)—better known as A3—and it’s now between Mars and Jupiter.
It could become as bright as Venus and be one of the best naked eye comets for years. Or, it might fizzle-out. Before it brightness another comet, called 12P/Pons–Brooks—which is similar to Halley’s comet—could also become easily visible.
Here’s everything you need to know about the possible next “Great Comet,” which will come closest to Earth in late 2024:
What is Comet A3?
Officially C/2023 A3 (Tsuchinshan-ATLAS), it’s a long-period comet with an orbit of just over 80,000 years. It comes from the Oort Cloud—a sphere around our solar system that’s home to millions of comets.
When was Comet A3 Discovered?
Comet A3 was discovered in February 2023 by astronomers ate both South Africa’s Asteroid Terrestrial-impact Last Alert System (ATLAS) telescope and China’s Tsuchinshan Observatory.
When Will Comet A3 be Visible?
The comet will make its closest approach to the Sun on October 10, 2024. It will be visible from the northern hemisphere most easily after that event, in the southwest just after sunset. It the weeks after it will climb higher into the southern sky where it should be a naked eye object.
How Bright Will Comet A3 be?
Some think comet A3 could undergo dramatic brightening to reach magnitude -5, which is about the same brightness as Venus. The full moon has a magnitude of -12.6 while the brightness of the sun is about -26.7, according to NASA.
That’s insanely bright and it’s only possible because of the relative geometry between our planet and this comet. The phenomenon at work here is forward-scattering of sunlight in Earth’s direction by dust and ice crystals in a comet’s coma and tail.
However, perhaps a magnitude of -1 is more sensible. In any case, when it’s at its brightest it will be lost in the horizon haze as seen from the northern hemisphere, only becoming naked eye when it’s dropped to magnitude -3 by mid-October 2024, according to Sky & Telescope. But that is still very bright for a comet!
Making a Plan to See Comet A3
Most comments require a lot of dedication, as usually some serious optics, such as large binoculars or telescope. However, if comment A3 truly does become a naked I come at all you will need to do to see it at its brightest and best is to look to the western sky after dark during December 2023. That doesn’t mean you shouldn’t take some special measures to get the best from it. The easiest way to get the best view of any naked eye, it is to get yourself under a dark sky close to a New Moon.
December 2023’s New Moon occurs on Dec. 12, making the week before and after ideal for comet-watching. However, if you want to make a night of it then be under a dark sky on Dec. 14/15, which is also when the annual Geminids meteor shower peaks.
What about 12P/Pons–Brooks?
A comet that orbits the Sun every 71 years, 12P/Pons–Brooks was first spotted in 1812. It’s due back in the inner solar system next year, sliding closest to the Sun on April 21, 2024 and making its closest approach to Earth on June 2, 2024.
Wishing you clear skies and wide eyes.