A new comet? Comet C/2024 G3 (ATLAS) is on the way...maybe

A Comet with the very poetic name of C/2024 G3 (ATLAS) is about to have a close encounter with the Sun and if it survives  - and this is a very big "if" - could be one of the most spectacular astronomy events of 2025. 

When was this Comet discovered and why do so many comets now seem to have "ATLAS" in their names?

It was found on the 5th of April 2024 by the automated Asteroid Terrestrial-impact Last Alert System (ATLAS) system. This is an asteroid impact early warning system that scans the entire sky every night looking for moving objects that could pose a threat to us folks here on Earth. It's one of several early warning systems against incoming hunks of space rocks. You can read more about the ATLAS program here.

As a result of scanning the sky so regularly and comparing it from night to night, the ATLAS program often finds comets when they are a long way from the Sun and appear as stars, giving away their true nature by the movement against the background of Milky Way stars. 

Why the big "if"?

Comet C/2024 G3 (ATLAS) is a sungrazing comet. Detailed observations revealed it to be a long period comet, meaning it's not a new arrival from the Oort cloud. It's visited the inner Solar System before. It will make its closet approach to the Sun, called perihelion, on January 13th, where it will be well within the distance that Mercury orbits the Sun at some 13.5 million km from our nearest star.

The very closeness of this approach to the Sun is what makes C/2024 G3 (ATLAS) an exciting object to track and follow. 

Comets are often referred to as "dirty snowballs", meaning they're loose clumps of water ice, frozen gases and other materials from the early stages of the Solar System. As they loop around the Sun during their orbit, some of this material is heated up and thrown into space. A thin atmosphere surrounding the comet expands into space where it can be seen as a fuzzy ball.  Material thrown away from the comet becomes the tail and shines either because of direct reflection of light from the Sun (a comet's dust tail) or because some of their gases are excited by the Sun's energy and emit their own light (the ion tail). It's not uncommon for comets to appear to have more than one tail, sometimes spreading at different angles to the comet itself.

Even though comets themselves are usually only a few dozen km in size, their brightly illuminated tails can stretch out over millions of kms, sometimes even being larger than the Sun itself. 

The behaviour of even regular cometary visitors to the inner Solar System can be hard to predict. Just how much material is thrown into space and how that will behave is an educated guess. It's even harder to say with certainty exactly how sungrazer comets will behave. As they travel close to the Sun, larger amounts of these comets are ejected into space and more likely to make a big splash in the sky.  Some of the most spectacular comets ever seen were sungrazer comets, such as Comet Lovejoy in 2011 and the even brighter Comet Ikeya–Seki in 1965.

The downside of skirting so close to the Sun is that comets can be completely torn apart by this journey and then drift off into space. We had high hopes for C/2024 S1 (ATLAS) last year, however it was demolished by the Sun. Read more about sungrazers here.

Sungrazing Comet Ikeya–Seki- in 1965 near Kitt Peak Observatory.  Image via  Roger Lynds/NOIRLab/NSF/AURA/ – taken on Kodak Ektachrome

We'll know shortly after C/2024 G3 (ATLAS) passes close to the Sun on January 13th whether it has survived somewhat intact and will be then visible in the coming weeks. 

What could I see and when can I this comet? (Assuming it scoots through ok...)

 It's estimated the comet will become visible in the evening sky in Australia from around the 16th or 17th of January, where it will be heading away from the Sun.

The spot in the sky where Comet Atlas (C/2024 G3) should be visible on the evening of the 17th January 2025 around 8.30pm. It will appear a little higher in the sky each evening and still be visible as the evening darkens, although it will also rapidly fade. 

It should appear as a bright spot with a tail fanning out away from the comet. Full Moon is on 14th January 2025 in Australia, so the Moon will be below the horizon when the comet is visible early in the evening and won't interfere with viewing. 

When will we know whether Comet C/2024 G3 (ATLAS) has it made around the Sun intact?

Given the potential for this comet, there will be a lot of interest about its behaviour after perihelion. We'll be keeping a close eye on any observations and sources like the Astronomer's Telegram and others for the latest news. I'll update this article as soon as we know more. 

What do I need to view this comet?

Our general advice with bright comets is to use binoculars. These give a nice wide field of view and are ideal for seeing the finer details of a comet's tail, especially if it's large and spread over several degrees. A telescope will give a close up views of a comet's coma, but won't be able to fit the tail into the field of view if it's spread over a larger part of the sky.

Nikon Aculon 10x42 binos at BINTEL - more info here. 

They don't need to be fancy either. Try the ones you have at home or look at the Nikon Aculon range here at BINTEL. These are affordable (starting at well under $200) and offer sharp clear view of the night sky and are ideal for day time viewing of birds, nature and sports. 

I've read this is the best comet of 2025. Why are folks saying this?

There are no periodic comets due to appear in skies for the rest of the year that will be bright enough to be seen with just your eyes, so yes, C/2024 G3 (ATLAS) could be the best comet of 2025. However, comets have a habit of surprising us and with any luck, the next Great Comet might dazzle us later in the year.

I'll be updating this article with more charts as more info becomes available. 

Cheers,

Earl White

BINTEL 

6th January 2025