Earth is set to gain a temporary “mini-moon” this autumn in the form of a small asteroid named 2024 PT5. The asteroid, about 33 feet (10 metres) wide, will orbit our planet for roughly two months, from September 29 to November 25, before escaping Earth’s gravitational pull.
The findings, published in the Research Notes of the American Astronomical Society, indicate that this rare occurrence highlights the dynamic activity of our solar system.
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Despite its status as a moon, 2024 PT5 will not be visible to the naked eye, as it is composed of dull rock. Even with binoculars or home telescopes, it will remain difficult to observe.
However, professional telescopes will be able to capture images of this asteroid as it passes by.
Astronomer Jennifer Millard, host of the Awesome Astronomy podcast, told the BBC’s Today programme, “Professional telescopes will be able to pick it up. So, you’ll be able to look out for lots of wonderful pictures online of this little dot moving past the stars at great speed.”
The asteroid, which was first spotted by Nasa’s Asteroid Terrestrial-Impact Last Alert System (Atlas) on August 7, hails from the Arjuna asteroid belt, which is a collection of diverse space rocks orbiting the Sun near Earth.
Mini-moons have visited Earth before. 2022 NX 1 orbited Earth briefly in 1981 and again in 2022. 2024 PT5 is expected to make a return in 2055, suggesting that Earth’s temporary companions often revisit after many years.
Temporary orbit and departure
According to scientists, 2024 PT5 will be caught by Earth’s gravity but will not complete a full revolution around the planet. As astronomer Jennifer Millard explained, “It’s just going to have its orbit altered, just twisted slightly by our planet and then it’ll continue on its merry way.” The asteroid is predicted to leave Earth’s orbit on November 25.
When asteroids like 2024 PT5 travel close to Earth at relatively slow speeds, the planet’s gravitational field can trap them temporarily. This is set to happen with 2024 PT5, which will orbit Earth for approximately two months.
Millard also noted the significance of such discoveries, saying, “This story highlights just how busy our solar system is and how much there is out there that we haven’t discovered… There are tens of thousands, if not hundreds of thousands, of objects out there that we haven’t discovered.” Mini-moons like 2024 PT5, often overlooked, demonstrate the importance of continuous monitoring of the night sky to discover these fleeting cosmic companions.