Move over, Moon – Earth is about to get a new natural companion. This "mini-moon" will be with us for the next two months, but this isn't its first visit, and it won't be the last, Science Alert reported.
This temporary mini-moon is actually a small asteroid, about 10m wide. Officially known as 2024 PT₅, the rock was only discovered last month, and path calculations suggest it will become Earth's satellite on September 29.
It will be our little companion for 56.6 days, completing one full orbit around the Earth. The rock will then break free from our gravitational tug on November 25th, returning to its path around the Sun.
2024 PT₅ will then pass by for the last time on January 9, 2025, coming within 1.8 million km of Earth before heading back into pitch darkness.
However, this is not the last time we will see 2024 PT₅. It is expected to return on November 8, 2055. It won't be as cozy the next time, however, as it will fly a distance of 5.2 million km.
This space rock was discovered on August 7 by the Asteroid Earth Impact Last Warning System (ATLAS), so it's good to know the mission is working as intended. This happened a day before it made its closest approach to Earth, passing just 567,000 km, which is 1.5 times the distance of the (normal) Moon.
Astronomers at the Complutense University of Madrid were then able to calculate the orbit of 2024 PT₅ using data from the JPL Small Body Database based on 122 observations over 21 days. This revealed that it is on a horseshoe-shaped trajectory and is moving relatively slowly, resulting in a short meso(mini-)moon phase with Earth.
Its orbital characteristics also helped the team determine where it might have come from. 2024 PT₅ appears to belong to a group of near-Earth objects called Arjuni, which orbit the Sun at roughly the same distance, shape and angle as Earth. This trajectory makes it unlikely that 2024 PT₅ is man-made space junk that ATLAS has spotted headed our way before.
This isn't the asteroid's first rodeo either. Astronomers traced its journey back 60 years into the past with a high degree of certainty before charting its fate and 30 years into the future. Outside of this period, the data become a bit more fuzzy due to the close interaction with the Earth-Moon system.
Before this year's approach, 2024 PT₅ made relatively close flybys in February 2003, April 1982, and March 1960. But on all three occasions, it was still chasing us at a distance of at least 8.2 million km. The last time it was within 1 million km appears to have been in October 1937, but as the team says, its history back that far is not so certain.
If we go backwards in time, the next sure visit will be in November 2055. After that, the nebulous crystal ball indicates that it may make another close pass in January 2084, about 1.66 million km away.
Earth has had similar brief encounters with mini-moons before. In 2020, astronomers realized that a small rock, no more than 3.5 m wide, had been orbiting our planet for about three years. Just a few months after her discovery, she broke free of her boundaries and moved away.
In 2016, another type of mini-moon was discovered. This one was a "quasi-satellite" in that it technically still orbited the Sun, but moved behind the Earth, entangled by its gravitational pull. It is estimated that she has followed us for almost a century and will probably follow us for several more. | BGNES
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