Excitement over 'comet of the century' - here's how and when to spot it

Tonight, stargazers will have the chance to spot what could be the most impressive comet of the year.

Comet A3, also known as Tsuchinshan-ATLAS, has come to be known as the “comet of the century” by excited astronomers, such is the anticipation about how bright and visible it might be.

People in the southern hemisphere have already had a glimpse of the comet, but, as it comes to within approximately 44 million miles of Earth from Saturday, it could also be seen in the northern hemisphere.

So what is Comet A3 and how likely are we to get a good view of it?

When was it discovered?

The comet was discovered independently in January 2023 by two observatories – China’s Tsuchinshan (Purple Mountain) Observatory and South Africa’s ATLAS (Asteroid Terrestrial-impact Last Alert System) – and was named after them.

It visits the inner solar system roughly every 80,000 years, so it would last have been visible from Earth when the Neanderthals were walking the planet.

Where is it from?

It comes from a place called the Oort Cloud, which, according to Dr Robert Massey of the Royal Astronomical Society (RAS), is “an incredibly large” distance from Earth, much further away than the planets and asteroids we are used to seeing.

The Oort Cloud is a “big, thick-walled bubble made of icy pieces of space debris the size of mountains and sometimes larger”, according to NASA.

It’s thought that most long-period comets, like the A3 comet, come from there.

When can it be seen?

It was visible between 27 September and 2 October, but as it loops back from the sun, the next couple of weeks offer a better chance to see it in the northern hemisphere.

Tonight, it will be at its closest point to Earth in its orbit so it’s a good time to try and catch a glimpse – although if you miss it, the comet should still be visible until 30 October.

Look to the southwest just after sunset, which is around 6pm in the UK.

“Savour the view,” said NASA astronomer Bill Cooke, because by early November, the comet will be gone again for the next 800 centuries.

How bright could it be?

Dr Massey warned that the “comet of the century” may prove to be no more than a nickname.

He said it’ll be a “nice comet” but probably less visible than NEOWISE was in 2020 or Hale-Bopp in the late 1990s – and many stargazers remember the latter as being a “really dazzling object”.

Mr Cooke said comets are often hard to predict because they’re extended objects.

He said if there is a lot of forward scattering – causing sunlight to bounce more intensely off all the gas and debris in the comet’s tail and its coma, it can make them easier for observers to see.

Can I get a picture of it?

Dr Massey suggests using “a good DSLR (digital single-lens reflex) camera” and trying for a set of exposures, as a lot of astrophotographers do.

If you have a good mobile phone camera and a small telescope, he said, you can “hold the mobile phone against the eyepiece of the telescope and try to take a picture that way”.

Dr Massey said that method “worked well with comets like NEOWISE and it might work well with this one, depending on how bright it is”.

“And if it’s genuinely easy to spot, you might be able to pick up your mobile phone, rest on something, and just point and shoot,” he added.

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What will happen to it afterwards?

MrCooke said Comet A3 isn’t expected to pass too near the planets, but eventually “could be flung out of our solar system – like a stone from a sling – due to the gravitational influence of other worlds and its own tenuous bond with the sun”.

But he said he “learned a long time ago not to gamble on comets. We’ll have to wait and see”.

Source: https://news.sky.com