A rare Sun-skirting comet will be visible from the southern hemisphere this week as it flies past Earth for the first time in around 100,000 years.
Astronomer Jonti Horner says the comet, also known as C/2024 G3 is, is “putting on an absolute show” for NASA’s space-based solar observatories.
Here’s how you too might catch sight of the comet over the next few days.
When can I see the Sun-skirter comet?
The comet will be visible until January 23, according to Dr Horner’s article in The Conversation.
He also told the ABC star gazers should choose their night based on the weather, as “it’s not a tomorrow-or-bust thing”.
The Bureau of Meteorology is predicting wet weather and cloudy skies for Australia’s Eastern states, but Dr Horner said he is planning on sneaking in a look of the comet on Saturday and Monday from south-east Queensland.
The best time to see the comet is just after sunset, he notes.
If you choose to see it on Thursday or Friday night, you could lose sight of it in the twilight glare. This is because it will “set” — or move below the horizon — only about 45 minutes after the Sun.
However, it may also appear brighter on those nights.
From the weekend onwards, it will appear higher in the sky and set an hour or more after the Sun.
“Even if the comet is a bit fainter I’d rather see it than not,” Dr Horner said.
To find it, try to situate yourself somewhere with a low horizon to the west. That is where you will be looking when you get comfy.
This view from the Night Sky Map for Sydney shows the position of the comet just before 9pm AEDT on January 18. (Reuters)
ANU astrophysicist Brad Tucker told Radio National on Wednesday to look about two o’clock from where the Sun sets, low in the sky.
He added that if you are looking higher than Venus, you have gone too high.
For anyone who struggles to identify the comet, you are looking for an “elongated triangle” appearing to be “escaping the Sun”.
Dr Horner recommends letting your eyes adjust to the darkness so you can see it against the night sky, but if you still find it difficult to spot you can use your camera or phone.
“They’re a bit more sensitive … and once you know where to look, the comet becomes a bit more obvious.”
What is a Sun-skirter comet?
C/2024 G3 is a Sun-skirter comet, meaning it is travelling close to the Sun.
At least in astronomical terms.
Dr Horner put it at 14 million kilometres from the Sun on Tuesday and called that “really close in”.
The comet barely seen at dawn from Montevideo, Uruguay on January 8. (Mariana Suarez)
Measuring at a few hundred metres to a few kilometres wide and made of frozen chunks of ice, the comet also gives off a stunning tail.
“These comets are really frozen chunks of ice. And it’s not just water ice,” Dr Tucker said.
” It’s a lot of methane ice, it’s a lot of carbon dioxide ice.
“As they get near the Sun, the Sun heats up that ice.
“The ice turns straight into a gas … and that’s what produces that beautiful tail.”
For comets of this size or smaller, the trip can be treacherous.
“Small comets that get that close to the Sun tend to fall apart because there’s so much stress, so much heat,” Dr Horner explained.
“This looked like it was going to be a small comet.
“So it was 50-50 whether it would survive and become fabulous or whether it would fall apart and be a disappointment.”
And if you are questioning why you might not have heard of this night-sky event sooner, Dr Horner speculated “nobody wanted to hype it too much” in case it was broken up before making it into visible space.
How often does it visit?
This comet previously skirted the Sun between 100,000 and 200,000 years ago, Dr Horner estimated, making this its second visit.
“That’s why I think it could be really promising,” he said
“It survived once. It should do so again.”
According to Dr Tucker, Sun-skirters “do one occasional trip into the solar system” with the more frequent flyers visiting every hundreds of thousands of years.
These are very different from Halley’s Comet or similar, which complete periodic orbits around the Sun.
Unlike their orbits, C/2024 G3 has a “weird, long-shaped” orbit where it gets pulled slowly towards the Sun then whisked right around and sling-slotted back out to the edge of the solar system over and over.
Before its first visit, astronomers believe C/2024 G3 originated in the vast Oort cloud of comets which stretches halfway between our solar system and the nearest star.
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“We think this one has been through at least once before,” Dr Horner added.
“It got nudged by a passing star, or tweaked by our galaxy’s gravitational pull, flung inwards,”
How much of a light show can we really expect?
An image of the comet taken from NASA’s orbiting Solar and Heliospheric Observatory. (Supplied: NASA SOHO)
Luckily, a come surviving a trip this close to the Sun is a “recipe” for it “becoming very bright”.
This is because the nucleus at the bottom of the tail is “jetting gas and dust into space in all directions” and the Sun — also known for jetting gas into space — is blowing all that matter away from it.
As a result, the comet’s tail is tens of millions of kilometres long.
Comparing it to Comet Tsuchinshan-ATLAS seen in October last year, Dr Horner said “it’s looking like it’s going to be about as good” in terms of visual appeal.
Still, he could not “100 per cent guarantee” viewers a good experience because comets are “like cats”.
“You can try and predict what they’ll do but they’ll do their own thing,” he says.
If you’ve got a Sun-skirter picture to share, we’d love to see them!
You can post them to the ABC-administered Weather Obsessed Facebook group or you can send them through our form below.
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