Brightening comet set to shine in autumn sky

Astrophotographer Max Inwood captured this long-exposure photo of the comet over Lake Pukaki, New Zealand

Astronomy fans, get your telescopes and cameras ready - it's possible an unusually bright comet is set to grace the night skies.

It should be visible in the northern hemisphere from about now, though it will be very low on the horizon before dawn.

But the best views are expected in mid-October, when it may even become visible to the naked eye.

Soon after it was first spotted there was speculation it could be one of the brightest comets in years. That excitement is fading, but it should still be something worth seeing.

The comet was first noticed in January 2023, by the Tsuchinshan Observatory in China, and later independently detected by Nasa's Asteroid Terrestrial-impact Last Alert System (ATLAS).

That helps explain its full name C/2023 A3 (Tsuchinshan-ATLAS). People are calling it Comet A3 for short.

Since then, astronomers have been tracking its progress, watching as it brightens and edges closer to its peak visibility.

Unlike asteroids, which are entirely made of rock, comets are composed of ice, rock, and gas.

As they approach the Sun, the warmth causes their ice to change into gases and release dust particles trapped in the ice, which is what causes their beautiful tail.

This latest comet has been visible in the Southern Hemisphere, and is now coming into view for the Northern Hemisphere too.

But it is notoriously difficult to guess how bright each comet will become.

Robert Massey, Deputy Executive Director of the Royal Astronomical Society, says: "Bright comets are quite rare, so if you do get a chance to see one, take a look, even if you have to use a pair of binoculars to pick out the tail and features. They're absolutely beautiful,"

Dr Massey remains sceptical about some of the expectations of this particular comet.

"Is it going to be the brightest comet in 100 years? I really doubt that," he says.

Will you be able to see the comet and how?

Dr Massey recommends looking for the comet during two periods.

For the next week or so it should be visible in the northern hemisphere low in the eastern sky before dawn, though you may need binoculars or a telescope.

There will be a better chance from around 12 October, this time after sunset in the western sky.

With some luck, you might even then spot the comet with a naked eye.

"You could go outside and say, 'Wow, there’s a comet!' without even needing binoculars," Dr Massey says.

"Comets are unpredictable, but we don’t know when the next one will appear, so don’t miss this chance," he adds.

With clear skies and the right conditions, this comet could provide one of the most captivating astronomical events of the year.

Although the comet may become as bright as Comet Neowise, which was a striking sight during the pandemic in 2020, scientists say it is unlikely to exceed that brightness.