Earth has a new cosmic sidekick, and it’s not your average moon. Astronomers have just confirmed the existence of a quasi-moon—a small asteroid named 2025 PN7, nicknamed “Arjuna”—that’s been quietly shadowing our planet for decades. This discovery is shaking up how we think about Earth’s neighborhood and the hidden dance of objects in our solar system.
What Is a Quasi-Moon, Anyway?
Unlike our familiar Moon, a
quasi-moon isn’t gravitationally bound to Earth. Instead, it’s an asteroid that orbits the Sun on a path so similar to Earth’s that, from our perspective, it seems to loop around us in a complex pattern. Think of it as a cosmic partner, moving in sync but never quite joining the family.
2025 PN7 was first spotted in August 2025 by the Pan-STARRS observatory in Hawaii. At roughly
20 meters wide—about the size of a small building—it’s been accompanying Earth since the 1960s, according to orbital simulations. Scientists expect it to stick around until
2083, making it one of the most stable quasi-moons ever found.
The Strange Orbit: A Celestial Figure-Eight
From Earth, 2025 PN7 appears to trace a
figure-eight or horseshoe pattern in the sky. This illusion is created by the combined gravitational pull of Earth and the Sun, keeping the asteroid near our planet for extended periods. Sometimes it drifts ahead of Earth, sometimes it lags behind, but it always maintains a delicate gravitational balance.
Unlike “mini-moons” that get temporarily captured by Earth’s gravity and then escape after a few months or years, quasi-moons like Arjuna can linger for
centuries. Their orbits are governed by a phenomenon called
mean motion resonance (MMR), which locks their orbital period to match Earth’s year almost perfectly.
Why Does This Matter?
The discovery of 2025 PN7 isn’t just a cosmic curiosity—it’s a scientific goldmine.
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Orbital Resonance: Studying quasi-moons helps researchers understand the gravitational choreography that keeps these asteroids in step with our planet.
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Space Missions: Their proximity and predictable paths make them ideal test subjects for future spacecraft, especially for practicing delicate maneuvers near small bodies.
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Solar System History: Quasi-moons could hold clues about the early history of the solar system and how small bodies evolve near planets.
Astronomers emphasize that 2025 PN7 poses
no threat to Earth. It stays millions of kilometers away from both our atmosphere and the Moon’s orbit, making it a safe companion for the foreseeable future.
Not Alone: Earth’s Growing Family of Quasi-Moons
2025 PN7 joins a select group of known quasi-moons, including
Kamo‘oalewa (2016 HO3) and
2023 FW13. Each new discovery adds to our understanding of how small objects move in the crowded gravitational neighborhoods around planets.
Other planets, like Venus and Neptune, also have quasi-moons, but Earth’s tally is growing—and the stability of Arjuna’s orbit makes it especially intriguing for scientists and skywatchers alike.
Can You Name a Quasi-Moon?
In a fun twist, there’s now an official competition to name one of Earth’s quasi-moons, with the requirement that the name be based on mythology. So if you’ve got a creative streak and a love for cosmic mysteries, this is your chance to leave a mark on the solar system.
The Big Picture: What’s Next for Quasi-Moons?
As astronomers continue to scan the skies, more quasi-moons may be waiting to be discovered. Each one helps refine our models of orbital stability, close approaches, and the safe operating zones for future missions. They also improve our understanding of meteoroid streams and the movement of material around the inner solar system.
For now, 2025 PN7 is a reminder that even in our own cosmic backyard, there are secrets waiting to be uncovered—and that the story of Earth’s companions is far from finished.
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