Earth will get a new mini moon this month

We had previously mentioned that, while in reality Earth really does have only one moon, but over time it has had other companions.

This fact is coming true at the end of this month when our home planet is going to get another companion satellite. This is what is called a temporary “mini moon”, which will arrive on September 29, 2024 and stay with us for around two months.

Our new companion is actually a newly discovered asteroid around 10 meters (33 feet) wide. Its official name is 2024 PT₅ and it was actually only discovered on August 7, 2024.

This space rock was discovered by the Asteroid Terrestrial-impact Last Alert System (ATLAS), just one day before it made its closest approach to Earth at just 567,000 kilometers (352,300 miles). Amazingly this is one and a half times the (normal) Moon’s distance.

Asteroid 2024 PT₅ will keep us company till November 25, and will complete one full orbit of Earth in about 57 days. On November 25, 2024 it will break away from Earth’s gravity and will complete its orbit around the Sun. Then it will return to circle our planet on January 9, 2025, when it will be very close to us (within 1.8 million kilometers (1.1 million miles) of Earth). Then it will head out again on its space journey.

Researchers at Madrid’s Complutense University analysed 122 observations of 2024 PT₅ over 21 days, using data from JPL’s Small-Body Database. This revealed its slow-moving, horseshoe-shaped orbit. This data indicated a brief mini-moon phase with Earth and suggested the asteroid belongs to the Arjuna group of near-Earth objects (which orbit the Sun at about the same distance, shape and angle as Earth), ruling out artificial space debris. The team successfully mapped the asteroid’s path 60 years into the past and 30 years into the future, though interactions with the Earth-Moon system make predictions beyond these timeframes less certain.

2024 PT₅ has visited us before, making a relatively close flybys in February 2003, April 1982 and March 1960 but then it was too far away, keeping a distance of at least 8.2 million kilometers (5.1 million miles). It was as far back as October 1937 that it came to less than a million kilometers away.

We will meet 2024 PT₅ again in about 25 years however. Astronomers expect it to visit us again on November 8, 2055, at which time it will fly by at a distance of 5.2 million kilometers (3.3 million miles). After which it might visit us in January 2084 at about 1.66 million kilometers (1 million miles) away.

Like we said before, Earth does get temporary satellites like mini moons. One small rock known as 020 CD3, just 3.5 meters (11.5 feet) wide, visited us for three years and was observed by astronomers in 2020, just before it went away.

In 2016, a unique type of mini-moon was identified—a ‘quasi-satellite.’ This intriguing object orbits the Sun while remaining closely tethered to Earth, caught in its gravitational influence. It is believed to have been accompanying us for nearly a century and is expected to continue doing so for several more years.

So go on, go outside and try to find 2024 PT₅ after September 29. It will be around for two months, so you’ve got a good chance!

The study of 2024 PT₅ was published in Research Notes of the AAS.

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Saima Baig

I am a Chartered Environmentalist from the Royal Society for the Environment, UK and co-owner of DoLocal Digital Marketing Agency Ltd, with a Master of Environmental Management from Yale University, an MBA in Finance, and a Bachelor of Science in Physics and Mathematics. I am passionate about science, history and environment and love to create content on these topics.