Astronomers have made an exciting discovery: a quasi-moon named 2025 PN7 has been hanging out near Earth for about 60 years without anyone noticing. This small space rock is special because it orbits the sun while staying close to our planet, completing its orbit in a year just like Earth does.
Quasi-moons are different from mini-moons, which only temporarily orbit Earth. For instance, in 2024, a mini-moon called 2024 PT5 made a brief appearance. Comparatively, 2025 PN7 belongs to a rare group that includes a few known quasi-moons, like Kamo‘oalewa, thought to be an ancient fragment of the moon. Notably, Kamo‘oalewa is one of the targets for China’s recent Tianwen-2 mission, set to return samples in 2027.
The Pan-STARRS observatory in Hawaii spotted 2025 PN7 on August 29. Researchers found that this object has actually been on an Earth-like orbit for decades. The rock is faint and small, making it easy to miss, according to Carlos de la Fuente Marcos, a researcher at Complutense University of Madrid. He noted that the quasi-moon is so elusive that it can only be seen when it’s close to Earth.
At its closest, 2025 PN7 comes within about 186,000 miles (299,337 kilometers) of Earth. For comparison, the average distance to the moon is about 238,855 miles (384,400 kilometers). “It’s a challenging object to observe,” de la Fuente Marcos explained. Finding such quasi-moons helps scientists learn more about the solar system.
Estimations suggest that 2025 PN7 is around 98 feet (30 meters) wide, but it could also be as small as 62 feet (19 meters). It is currently the smallest known quasi-moon orbiting near Earth. Interestingly, this space rock changes its orbit between two types: a closer elliptical path and a far-reaching horseshoe orbit. It’s expected to stay in its current orbit for another 60 years before being pulled back by the sun’s gravity.
What’s still unclear is the rock’s exact composition. Most likely, it is a natural asteroid rather than leftover satellite debris, indicated by its orbit’s behavior, says Dr. Teddy Kareta from Villanova University. He noted that bad weather has hindered his attempts to study it directly.
As scientists contemplate 2025 PN7’s origins, de la Fuente Marcos theorizes it came from the Arjuna asteroid belt, which consists of small rocks that share similar paths with Earth. This could explain how material from lunar impacts might contribute to quasi-moons and mini-moons.
Despite their close orbits, 2025 PN7 and similar objects don’t generally pose a danger to Earth. Future missions, like the one aimed at Kamo‘oalewa, could unlock even more secrets about these fascinating celestial bodies. Exploring these relatively easy-to-reach asteroids could provide insights into planetary exploration without a hefty investment.
For more information on quasi-moons and related asteroid research, you can check out NASA’s resources on near-Earth objects here.
