Astronomers discover new quasi-moon orbiting the Earth

For more than sixty years, a tiny asteroid has been moving in step with Earth, hidden from view until recently. Astronomers now confirm that this small body, named 2025 PN7, is traveling in a special type of orbit called a quasi-satellite path. Unlike the Moon, which is locked in Earth’s gravity, this rock is really orbiting the Sun. But from Earth’s perspective, it appears to loop around us like a second moon.

The discovery of 2025 PN7 adds another curious member to a small club of objects that trail our planet through space. And while this one is likely to stick around for only a few more decades, its presence offers fresh insight into how gravity works in the complex dance between Earth, the Sun, and near-Earth asteroids.

A quasi-satellite is a kind of orbital trick. The object circles the Sun almost in lockstep with Earth, so from our point of view it seems to orbit us. In reality, the Sun is still the main force steering its course. When tracked from Earth, these paths often look like looping or corkscrew patterns in the sky.

Astronomers have known about quasi-moons since the early 1990s, when the asteroid 1991 VG was first spotted and briefly thought to be an alien probe. Since then, several others have been identified, including Kamo‘oalewa, which has been shadowing Earth for hundreds of years and may stay in its orbit for centuries more.

The newest addition, 2025 PN7, is the smallest and least stable of the group. At just 62 feet across—about the size of the meteor that exploded over Chelyabinsk, Russia, in 2013—it is faint, with a brightness that makes it invisible without powerful telescopes.

The asteroid was first seen on August 2, 2025, by astronomers using the Pan-STARRS1 telescope at Haleakalā Observatory in Hawaii. Its unusual orbit caught the attention of Adrien Coffinet, a French journalist and amateur astronomer, who ran calculations showing it might be a quasi-satellite. He shared his findings with the Minor Planet Mailing List, sparking further study.

Researchers Carlos de la Fuente Marcos and Raúl de la Fuente Marcos of the Complutense University of Madrid quickly took a deeper look. Using NASA’s Jet Propulsion Laboratory Horizons system and Python-based modeling, they mapped the object’s orbit and compared it to other quasi-moons. Their results were published in the journal Research Notes of the American Astronomical Society.

Their analysis showed that 2025 PN7 has been in this strange orbit for about 60 years already and will likely remain there for another 60. After that, its path will probably shift away from Earth. In total, its stay as a quasi-satellite will last about 128 years—short compared with Kamo‘oalewa’s 381-year span, but long enough to give scientists plenty of time to study it.

One of the first questions asked about 2025 PN7 was whether it poses any risk to Earth. The answer, for now, is no. Models show that its distance from our planet fluctuates but never comes close enough to threaten a collision.

Still, its orbit is not especially stable. Small factors, like the pressure of sunlight or slight gravitational nudges from other planets, can slowly shift its trajectory. These effects make it hard to predict exactly how the story will end. At some point, the asteroid will drift out of its quasi-satellite role, possibly moving into a different co-orbital path before heading off into space.

Studying quasi-moons like 2025 PN7 helps astronomers understand how small objects behave when influenced by both Earth and the Sun. These asteroids serve as natural experiments in orbital mechanics, showing how gravitational forces shape paths over decades or centuries.

Tracking them also supports planetary defense. Even though 2025 PN7 is not dangerous, keeping tabs on objects that linger near Earth is vital for spotting any that might pose a real threat in the future. The work sharpens tools used to predict and evaluate asteroid hazards.

Quasi-satellites may also prove useful for space exploration. Because they remain close for extended periods, they could become practical targets for robotic missions. Sending a probe or sample-return mission to a quasi-moon would be less costly than chasing down an asteroid that only passes Earth once in a while. Some researchers even suggest that in the distant future, such objects could play a role in asteroid mining.

So why did it take six decades for astronomers to notice 2025 PN7? The answer lies in its size and faintness. At magnitude 26, it is millions of times dimmer than stars visible to the naked eye. Combined with unfavorable viewing angles, the asteroid managed to escape detection until now.

Carlos de la Fuente Marcos stated: “It is small, faint, and its visibility windows from Earth are rather unfavorable, so it is not surprising that it went unnoticed for that long.”

With new observatories such as the Vera C. Rubin Observatory coming online, more quasi-satellites may soon be uncovered. This next-generation telescope can scan the sky with unprecedented depth and frequency, making it possible to spot dim and fleeting objects that once slipped past unnoticed.

It’s worth noting that quasi-moons are not the same as “mini-moons.” Mini-moons are asteroids that get temporarily captured by Earth’s gravity and truly orbit the planet for a time before escaping. Quasi-satellites like 2025 PN7 never cross that line. They only appear to circle Earth while actually moving around the Sun.

At present, scientists recognize six other quasi-moons: 164207 Cardea, 469219 Kamo‘oalewa, 277810 (2006 FV35), 2013 LX28, 2014 OL339, and 2023 FW13. Each has its own unique orbital quirks and lifespan as an Earth companion. Adding 2025 PN7 to this list broadens the picture of how diverse these temporary neighbors can be.

Astronomers will continue to track 2025 PN7 to refine predictions about its future path. With each new observation, uncertainties about its stability will shrink. The asteroid’s behavior may even help identify the best ways to find and classify other quasi-moons.

As telescope technology improves, what once seemed like rare oddities may turn out to be fairly common. For now, though, Earth’s newest companion offers a reminder that our cosmic neighborhood is full of surprises.

Note: The article above provided above by The Brighter Side of News.

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