2023 has proved a real treat for astronomy fans so far. Cosmic spectacles have been decorating the skies in recent weeks, with the stunning Quadrantids meteor shower in early January and the asteroid that came relatively close to the Earth (albeit still 2,200 miles away) last week.
And the show isn’t over. Now stargazers can expect to see a green comet passing Earth for the first time in 50,000 years – meaning the last time it might have been visible from this planet was during the Stone Age.
Named C2022 E3 (ZTF), the approaching comet was first detected back in May 2022 and after reaching its closest point to the Sun on January 12, it will finally be visible from Earth this week at 26 million miles away. If you want to catch sight of it, you’re going to have to plan head. Fancy catching this once-in-a-lifetime event? Here’s everything you need to know.
What is a green comet?
Sometimes referred to as ‘cosmic snowballs’, comets orbit the sun and are a combination of frozen gases, dust and rock.
As they soar closer to the sun, they are subject to blasts of radiation, which releases gases and debris. It isn’t the comet itself but the atmosphere surrounding it – known as the ‘coma’ – that glows green as a result.
When can I see the green comet?
According to experts, the best time to see the comet in the UK will be early Thursday morning (February 2) at around 4am, when cloud cover is minimal (according to weather forecasts from the Met Office).
When will the green comet be closest to Earth?
The comet will get closest to Earth on Thursday. It’ll be around 26 million miles away – around 109 times the average distance of the moon – but will burn so bright that will likely still be visible in the night sky.
Why is the comet green?
The green glow apparently arises from an interaction between light from the sun and diatomic carbon, which is formed on the head of the comet when larger carbon-based substances are broken down by sunlight.
When the diatomic carbon interacts with ultraviolet rays, it gives off light, resulting in the green colour surrounding the nucleus of the comet.
What time will the green comet be visible in the UK?
In the UK, people are advised to get out in the early hours of February 1 and look towards the north-east horizon in order to catch a glimpse of the flyover. You can try again just before dawn on February 2.
How can I watch the green comet?
As it nears Earth, there is a chance that the comet will be visible with the naked eye as a bright white smudge in the sky. For the best view, though, NASA advises that stargazers get their hands on a telescope or a pair of binoculars. Although it’s unlikely that you will be able to see the green glow this way, if you look closely you may catch a glimpse of the comet’s yellowish tail.
The SkyPortal app, available on Apple and Android phones, can help direct you to the right spot in the sky. Simply download the app, select the Search icon, tap on Bright Comets and C2022 E3 (ZTF) will appear as an option.
Other nifty ways of locating it include this map and this finder chart.
If you fancy watching the comet without having to endure the cold, The Virtual Telescope Project is also hosting a free live-stream following its voyage.
What is special about this comet?
This really is a once-in-a-lifetime event. The last time the comet passed Earth was during the last Ice Age, and it won’t be seen again for another 50,000 years (when it restarts its orbit around the sun).
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