‘Brighter than expected’ comet may be visible without telescope this week

Skygazers in southern hemisphere are already sharing pictures of comet A3 on social media

A recently identified comet is growing “brighter than expected” and could be the most impressive one of the year for skygazers, astronomers say.

Tsuchinshan-Atlas, discovered in 2023 and simply known as A3, has been making its way into the inner Solar System and is now visible in several regions of the world.

The comet comes from the Oort cosmic debris cloud enveloping the Solar System and is named after the two observatories that independently discovered it.

“We may be in for a much brighter comet than predicted,” Nick James of the British Astronomical Association said.

Skygazers in Australia and several other countries in the southern hemisphere are already sharing pictures of the comet on social media, revealing it is getting brighter and more colourful with the early morning Sun in its backdrop.

Lucy Yunxi Hu from Australia: "Comet C/2023 A3 Tsuchinshan-ATLAS over Lake George. It is presented as a time slice, taken on the morning of September 21, 2024. The image was shot during the blue hour (between 4:28 and 4:53 am local time)." Thank you, Lucy!https://t.co/x7hmROxmAY pic.twitter.com/9qcSgF4abz

— EarthSky (@earthskyscience) September 25, 2024

The comet could grow brighter still and become a “naked-eye object” as it gets closer to the Sun in October.

“The change of the comet compared to yesterday has been exponential,” Frank Rodriguez, who spotted the comet over Gran Canaria Island just before sunrise, told Space Weather.

A3 is expected to grow brighter and appear higher in the morning sky of the southern hemisphere until 27 September, after which it could gradually become obscured by the Sun and harder to spot.

Comet C/2023 A3 (Tsuchinshan-ATLAS) is finally here ! ☄️✨I captured this image this morning at 09:22 UTC from @LCOAstro in Atacama desert in Chile 🇨🇱 The view was absolutely spectacular ! The clouds were constantly moving just above the horizon, but we got really lucky when the… pic.twitter.com/AoClHkatFr

— Yuri Beletsky (@YBeletsky) September 24, 2024

It may again become easier to see in the evening sky from around the middle of October.

As A3 makes its closest approach to the Sun on 27 September – likely its only encounter with the star – it could eventually reach a brightness rivalling the glow of some of the brightest stars in the sky, astronomers say.

The comet’s closest approach to Earth takes place between 12 and 13 October 2024, astronomers estimate.

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

But exactly how bright it could get over the next month is currently unknown as it depends on how much gas and dust the comet’s nucleus would expel.

Comet visibility can be unpredictable as they tend to break up sometimes and fail to glow as brightly as expected.

If A3 survives the journey closer to the Sun between Friday and early October, skygazers in the northern hemisphere may see it shining in the east – low on the horizon – just before sunrise, experts say.

Some optimistic estimates suggest that the comet may even become one of the brightest in many years.