Meet Earth’s new travel buddy: A tiny quasi-moon that’s been following us for decades

The Earth has a new follower. Astronomers recently discovered a tiny quasi-moon that they believe has been orbiting the sun alongside the Earth for decades.

The new quasi-moon, which is being called 2025 PN7, was first spotted this summer by scientists at the University of Hawaii. Its exact size is difficult to determine, but it’s clear that it’s very small — at least on the scale of space objects. One estimate puts it at about 60 feet across, while others suggest it could be more than double that.

What is a quasi-moon?

Quasi-moons are not really moons. They’re asteroids. Unlike our actual moon, they aren't gravitationally bound to the Earth. Instead, they are objects that happen to fall into the same orbital path that the Earth takes around the sun, like two separate boats floating down the same stream.

“The Solar System is full of surprises, so we keep looking,” Carlos de la Fuente Marcos, a researcher who co-wrote a new study on 2025 PN7, told CNN.

Quasi-moons don’t join Earth’s orbit indefinitely. They tend to tag along for a relatively brief period of time. This newest one is believed to have partnered up with the Earth about 60 years ago and is expected to spin off on its own in 2083.

Because they are so small and tend to be too dim to spot on a telescope, quasi-moons weren’t discovered until the early 1990s. With this new addition, there are now eight known quasi-moons speeding through space alongside the Earth.

A quasi-moon’s relationship to the Earth isn’t static. It can change its relative position significantly over time. At its closest, astronomers estimate that 2025 PN7 came within about 2.5 million miles of Earth — about 10 times the distance between the Earth and the moon. At other points, it has been as far as 11 million miles away.

Why astronomers love quasi-moons

The discovery of anything new in space is always worth celebrating, but there’s extra enthusiasm when a quasi-moon is found. That’s because quasi-moons, thanks to their unique orbits, provide the rare opportunity for scientists to study a single object for an extended period of time.

“Their cycling around Earth allows even very small asteroids like this one to be studied for years, and often decades, as they repeatedly come back to visit us every single year,” amateur astronomer Sam Deen told the astronomy magazine Sky & Telescope.

Most asteroids speed by the Earth so quickly that astronomers have only a limited time to study them. Quais-moons stay nearby for years or even decades, making them ideal subjects for long-term study. In May, China launched a probe called Tianwen-2 on a mission to land on a quasi-moon called Kamo'oalewa and bring geologic samples back to Earth for study.