Astronomers have found a space rock that has been quietly hanging around Earth for decades: a tiny asteroid named 2025 PN7. This so-called “quasi-moon” isn’t a true moon or a mini-moon, because it orbits the Sun rather than our planet. But its orbit is so similar to Earth’s that it will be our companion for around another 60 years.
Though the quasi-moon orbits the Sun, it occasionally looks from our vantage point like it is looping around us. However, our orbits are slightly different, so sometimes it lags behind us and sometimes it seems to lead us. But since the little asteroid’s orbit around the Sun is very close to one Earth year, it is always pretty close.
2025 PN7 is just 19 meters across and might be the smallest quasi-moon ever found. Its minuscule size means that it can be quite tricky to spot. As astronomers put it, its “visibility windows” are very narrow. We can only see it through very large telescopes when its position and the lighting are favorable. That’s partly why it evaded detection for so long.
Entered orbit in 1957
Although the Pan-STARRS1 telescope in Hawaii discovered it in August 2025, the quasi-moon has been in this orbit for far longer. When researchers later trawled through archived images, they found that 2025 PN7 had shown up decades earlier. They think it likely entered its current orbit in 1957.
It won’t stay with us in this dance forever. Simulations suggest that it will keep up company for another 60 years before it wanders off in another direction. In that time, its distance from Earth will change quite a bit. So far, it has varied between 4 million kilometers at its closest and 18 million kilometers at its furthest.
2025 PN7 is one of seven quasi-moons in Earth-like orbits, and seems to be the smallest and least stable. Astronomers aren’t exactly sure where it came from. It does not pose any threat to us.
“These asteroids are relatively easy to access for unmanned missions and can be used to test planetary exploration technologies [relatively cheaply],” said Carlos de la Fuente Marcos, lead author of the study.
