Astronomers Uncover Mysterious ‘Quasi-Moon’ Secretly Shadowing Earth’s Journey Around the Sun
Imagine discovering an old friend who’s been tagging along on your cosmic road trip for over seventy years — and you didn’t even know it. That’s precisely what astronomers unveiled with asteroid 2025 PN7, a quirky little “quasi-moon” that’s been quietly orbiting the Sun in Earth’s company since the 1950s. Not quite a moon, not quite a stranger, it’s been keeping pace with our planet like a cosmic buddy system, and it’s set to stick around for another six decades before it heads back out into the vastness of space. What’s so special about a quasi-moon, you ask? Well, unlike our trusty satellite, these sneaky space hitchhikers don’t orbit Earth directly; instead, they dance in a gravitational jig with our planet — sometimes leading, sometimes lagging — giving the illusion they’re circling us when they’re really just sun-chasers locked in step. Intrigued by these celestial tagalongs who might just hold clues to the early solar system — or maybe a hint that Earth has more neighbors than we thought? Buckle up, because 2025 PN7 is just the tip of the quasi-moon iceberg.
The asteroid, 2025 PN7, has seemingly been orbiting the Sun alongside Earth since the 1950s, and it will likely stay on its track for another 60 years before it travels back out into space.
JPL-Caltech/NASAAn artist’s impression of the newly discovered quasi-moon.
Astronomers have discovered a new object traveling with Earth around the Sun — an asteroid known as a “quasi-moon.”
This small celestial object, designated 2025 PN7, was first detected on August 2 at the University of Hawaii’s Pan-STARRS observatory. At an estimated 62 feet across, the faint object had gone unnoticed for years, but scientists have since found earlier images of it dating back several years. Its unusual orbit means it has likely been accompanying Earth for decades, and it may continue to do so for years to come.
What Makes A Quasi-Moon Special?
Unlike Earth’s Moon, which is gravitationally bound to Earth, quasi-moons orbit the Sun while keeping pace with Earth.
As these asteroids trace their orbits, they are slightly affected by Earth’s gravity, too. They don’t circle Earth like satellites, but their orbits do fall into a kind of lockstep with our planet that keeps them close by. It’s what The Planetary Society’s Asa Stahl calls a “gravitational sleight of hand.”
Addy Graham/University of ArizonaAnother artist’s impression of a quasi-moon around Earth.
This creates what scientists call quasi-satellite motion, in which the asteroid sometimes drifts ahead of Earth and sometimes trails behind it, creating the appearance from our perspective that it’s orbiting us rather than the Sun. Astronomers also emphasized that quasi-moons are distinct from “mini-moons,” which are temporarily captured by Earth’s gravity, or Trojan asteroids, which sit in gravitationally stable points ahead of or behind a planet.
A paper detailing the new quasi-moon was published in the journal Research Notes of the American Astronomical Society (AAS) on Sept. 2.
Earth’s Growing Family Of Pseudo-Moons
The newly identified quasi-moon, 2025 PN7, belongs to a rare group of near-Earth objects called Arjuna asteroids, which have Earth-like orbits. The asteroid is dim, with an absolute magnitude of about 26. That makes it difficult to observe even with powerful instruments.
Its small size and faintness likely explain why it escaped detection until now.
Earth hosts seven known quasi-moons, with this latest discovery adding to our understanding of these temporary cosmic companions.
All of Earth’s known quasi-moons are transient visitors that will eventually transition to different orbital configurations after hundreds or thousands of years. Some will shift to “Trojan” orbits, following points that stay consistently ahead of or behind Earth, while others may adopt “horseshoe” orbits that alternate between leading and trailing our planet.
2025 PN7 joins notable companions like 469219 Kamo’oalewa, which has garnered significant scientific attention since its discovery in 2016.
NASAEarth’s orbit around the Sun (blue) contrasted with the orbit of quasi-moon 469219 Kamo’oalewa (yellow).
Since quasi-moons orbit close to Earth and are often quite small, they would also be easier to visit and redirect than most other asteroids. This accessibility makes them ideal targets for sample return missions and detailed studies. China, for example, launched its Tianwen-2 mission to Kamo’oalewa in May 2025 to collect samples, investigate the asteroid’s composition, and potentially reveal its origins.
Quasi-moons may also preserve clues about the early solar system. Some researchers suspect certain quasi-moons could be fragments ejected from the Moon or debris from past collisions. Determining their composition through spectroscopy could shed light on their origins.
By comparison, 2025 PN7 is smaller and less stable than Kamo’oalewa, but its discovery demonstrates that Earth may have more unseen neighbors drifting nearby.
No Threat To Earth
JPL-Caltech/NASAPN7’s orbit closely follows that of Earth.
Despite their proximity and size, these quasi-moons pose no immediate danger to our planet. Scientists used to think certain quasi-moons had a significant chance of impacting Earth, but that’s no longer the case.
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