Earth set to obtain ‘second moon’ tonight that won’t be seen again until 2055
Our planet is set to gain a second, 'mini-moon' tonight (29 September), which will stick around for a couple of months.
The space rock is part of the Arjuna asteroid belt, which is not too far from Earth by space terms, just 2.8 million miles (4.5 million kilometres) away.
It's called 2024 PT5 and it helps to make up the population of asteroids and comets that are monitored by some of the finest minds in astronomy, at the NASA-funded Asteroid Terrestrial-impact Last Alert System (ATLAS).
The asteroid will not complete a full orbit around Earth though, despite getting caught in its orbit and being given the title of a 'mini-moon'.
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What is a 'mini-moon'?
It can be defined as a 'temporarily captured object', as the modestly sized 2024 PT5, with a diameter of roughly 11 metres (the same as a London bus), will stay in orbit for a couple of months before making its way through our Solar System.
The asteroid will orbit our blue planet in a horseshoe-shape, starting on 29 September and going until 25 November.
After escaping from our world's orbit, it will return to a heliocentric orbit, which is around the Sun - like what we do.
However, it's predicted that the space rock will not come into Earth's orbit again until 2055.
How can I see the mini-moon?
Sadly, if you're not a professional, chances are you won't be able to see it for yourself.
The event can't be seen by the naked eye, binoculars or with a consumer-grade telescope, as the mini-moon will have a magnitude of 22 (incredibly low on the -10 to +20 scale), meaning it will be too faint to see.
You'll need high-tech equipment but even then, some observatories have revealed to The Sun that professional telescope will also struggle to detect 2024 PT5.
Who discovered the new mini-moon?
First discovered by the ATLAS telescope on 7 August in South Africa, the Arjuna rock is known as a near-Earth asteroid (NEA).
Arjuna asteroids orbit the Sun on an orbital path that stretches out a bit further into the Solar System compared to our planet's path, though some may come close to the Earth-Moon system.
Have there been other mini-moons?
The short answer is yes.
In our time observing space, 2024 PT5 has not been the first mini-moon collected by out planet, as it is known to capture and pull NEAs into its orbit.
Back in February 2020, a tiny asteroid named 2020 CD3 was found to have been orbiting Earth for a few years, before leaving our orbit the following month.
In 2016, there was an object called 2016 HO3, which was 40-100 metres in diameter, though it did not orbit the Earth so it was not a moon - but it oddly moved in sync, looking like it was orbiting our planet but it was really orbiting the Sun.
Joshua Nair