Green comet: How to see once-in-a-lifetime comet C/2022 E3 from the UK
By ITV News Digital Content Producer Elaine McCallig
A once-in-a-lifetime comet could be visible with the naked eye as it lights up the night sky on Wednesday.
Comet C/2022 E3 (ZTF), or the "green comet", was last visible from earth during the Stone Age and won't be visible again for an estimated 50,000 years.
It made its closest approach to the sun on 12 January, and is due to pass closest to Earth on Wednesday night, into the early hours of Thursday and in a very dark sky will appear as a faint smudge to those looking for it with the naked eye.
What is Comet C/2022 E3 (ZTF)?
The comet was discovered within Jupiter's orbit by astronomers at the Zwicky Transient Facility in California in March 2022.
At the moment, it resembles a "fuzzy green ball in the sky". The comet emits a green glow due to UV radiation lighting up the gases streaming off the comet's surface, the Royal Observatory says.
The celestial body has continued to grow brighter throughout January.
Comets are unpredictable, so it's difficult to predict exactly what to expect next Wednesday. The comet isn't expected to form a tail that can't be seen without a telescope, but that could change.
One of the scientists that discovered the comet, Bryce Bolin, told the Boston Globe that it will look like a white smudge in the sky just north of the Little Dipper constellation.
“Comets are the cats of the solar system; they do whatever they want,” Mr Bolin said. “Like cats they have fluffiness. Comets have been observed to have peculiar behaviours, like fragmenting or disintegrating.
"But there is not really a strong correlation between the distance to the sun and the kind of disintegration events that occur. It could break apart on its way in before it ever comes close to the sun, or even after."
He added that they "secretly hope it will disintegrate" as "that's where the most interesting science is".
How to see Comet C/2022 E3 (ZTF) in the UK
The comet is already visible in the northern hemisphere using a telescope or binoculars, but as it gets brighter and closer it may be visible with the naked eye on Wednesday, the Royal Observatory says.
"Comets are notoriously unpredictable, but if this one continues its current trend in brightness, it'll be easy to spot with binoculars, and it's just possible it could become visible to the unaided eye under dark skies," Preston Dyches from Nasa's Jet Propulsion Laboratory said.
In the northern hemisphere, the comet should be visible in the morning sky as it moves swiftly towards the northwest during January. It will be visible in the southern hemisphere in early February.
He added: "This comet isn't expected to be quite the spectacle that Comet Neowise was back in 2020. But it's still an awesome opportunity to make a personal connection with an icy visitor from the distant outer solar system."
When it streaks through our skies in February, it will be in the constellation of Camelopardalis. After its closest approach, it will move through Auriga and end up in Taurus by the middle of February.
To give yourself the best chance of viewing the comet, the Royal Observatory suggests allowing your eyes to adjust to the dark for at least 15 minutes and avoid looking at bright devices, such as your phone.
By checking what time the moon will rise in your area and looking skyward before it rises, you can avoid the moon's light polluting your view of the comet.
Most astronomy apps will be able to help you track the comet, but University of Toronto astrophysicist Hanno Rein created an Apple app especially for locating and tracking Comet C/2022 E3 (ZTF).
If you're unable to spot it in the sky yourself, The Virtual Telescope Project will stream the event from 0400 GMT on February 1 on the project's YouTube channel.
Want a quick and expert briefing on the biggest news stories? Listen to our latest podcasts to find out What You Need To Know