Earth will welcome a new companion this autumn: a small asteroid is going to be captured in our gravitational pull on Sunday and temporarily become a “mini moon,” according to multiple media reports.
Arriving 29 September, the asteroid known as 2024 PT5 will stick around until late November before escaping Earth’s gravity again. It was first spotted by US space agency NASA on 7 August, having emerged from the Arjuna asteroid belt. Arjuna asteroids are considered near-Earth objects thanks to their orbits, which are quite similar to Earth’s, and they occasionally get as near as 4.5 million kilometres from our planet. (For reference, the Moon is 384,400 kilometres away and Venus, our closest planetary neighbour, about 24 million kilometres away at its nearest point in orbit.)
The asteroid isn’t going to stick around long enough to complete a full revolution of our planet, Dr Jennifer Millard, astronomer and host of the Awesome Astronomy podcast told the BBC. It will just have its orbit “twisted slightly by our own planet and then it’ll continue on its merry way.”
[See more: ‘Milestone’ mission: China is poised to land on the far side of the moon]
That Earth’s gravitational pull can trap it at all is due to proximity and the asteroid’s relatively slow speed of around 3,450 kilometres per hour. It’s also fairly small, just 10 metres long, and made of dull rock which means it won’t be visible even with binoculars or a home telescope.
Millard reassures space enthusiasts that professional telescopes will be able to pick up 2024 PT5 so be on the “look out for lots of wonderful pictures online of this little dot kind of moving past the stars at great speed.”
Scientists predict that 2024 PT5 will swing back around to our planet in 2055. But this isn’t the first mini moon to be pulled in by Earth, or even the first to make a repeat visit. The asteroid 2022 NX1, for example, made its first appearance (that we know of) in 1981 only to return again in 2022.
