Earth to gain second 'moon' for nearly two months as asteroid expected to enter orbit
28 September 2024, 14:02
A small asteroid is going to be captured by Earth’s gravitational pull and temporarily become a "mini-moon" this autumn, according to scientists.
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The asteroid is expected to orbit from 29 September before escaping from Earth's gravity again on 25 November.
Unfortunately, the second moon is going to be too small and dim to be seen without a professional telescope.
The asteroid was first spotted by NASA’s Asteroid Terrestrial-Impact Last Alert System (ATLAS) on 7 August before scientists worked out its trajectory in a study published in Research Notes of the American Astronomical Society.
The asteroid, referred to by scientists as 2024 PT5, comes from the Arjuna asteroid belt, which contains rocks that follow an orbit quite similar to Earth’s.
Occasionally, some of these asteroids get relatively close, getting as near as 2.8 million miles (4.5 million km) from our planet.
According to the researchers involved in the study, if an asteroid like this is moving at a relatively slow speed of around 2,200mph (3,540km/h), Earth’s gravitational field can exert a strong influence, enough to trap it temporarily.
Dr Jennifer Millard, astronomer and host of the Awesome Astronomy podcast, told the BBC: "It's not going to complete a full revolution of our planet, it's just going to kind of have its orbit altered, just twisted slightly by our own planet and then it'll continue on its merry way," she said.
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The asteroid is approximately 32ft (10m) long, which is tiny in comparison to Earth's moon, which has a diameter of approximately 3,474km.
"Professional telescopes, they'll be able to pick it up. So you'll be able to look out for lots of wonderful pictures online of this little dot kind of moving past the stars at great speed," said Dr Millard.
Mini-moons have been spotted before, while some even come back for repeat visits and it's thought many more are likely to have gone unnoticed.
The 2022 NX1 asteroid became a mini-moon in 1981 and again in 2022 while scientists predict 2024 PT5 will also return to Earth’s orbit again in 2055.
Dr Millard said: "This story highlights just how busy our solar system is and how much there is out there that we haven't discovered, because this asteroid was only discovered this year.
"There are tens of thousands, if not hundreds of thousands, of objects out there that we haven't discovered and so I think this highlights the importance of us being able to continually monitor the night sky and find all of these objects.”
