We cannot determine its true size with precision
The asteroid 2025 PN7, discovered in August 2025, is possibly the smallest quasi-moon ever recorded, traveling in Earth's orbital lane around the Sun. Scientists cannot yet determine the asteroid's origin or exact size due to limited telescopic observations, with estimates ranging from 16 to 49 meters.
- Asteroid 2025 PN7 discovered August 2025, estimated 16 meters wide
- Has orbited Earth since 1957, will depart around 2083
- Closest approach: 4 million kilometers; farthest: 17 million kilometers
- May be the smallest quasi-moon ever recorded
Astronomers detected asteroid 2025 PN7, a quasi-moon estimated at 16 meters wide, that has been following Earth's orbit since 1957 and will depart in approximately 60 years.
Astronomers announced this summer the discovery of a small asteroid that has been traveling alongside Earth for nearly seven decades without anyone noticing. The object, designated 2025 PN7, was first spotted in August using the Pan-STARRS observatory in Hawaii, but once researchers examined archival images, they realized it had been shadowing our planet since 1957—the same year the Soviet Union launched Sputnik, humanity's first artificial satellite. The asteroid is what scientists call a quasi-moon: a space rock that orbits the Sun in lockstep with Earth, maintaining a stable position relative to our planet rather than circling it directly.
The discovery is remarkable partly because of what the asteroid is not. At an estimated 16 meters across—shorter than a bowling lane—it may be the smallest quasi-moon ever documented. Measuring such distant objects is imprecise work. Astronomers calculate size by analyzing how much light bounces off the surface, but because 2025 PN7 is difficult to observe, estimates range as high as 49 meters. Carlos de la Fuente Marcos, an astronomer at the Complutense University of Madrid who led the study published in the Research Notes of the American Astronomical Society, acknowledged the uncertainty. "We cannot determine its true size with precision," he explained. Future observations may narrow the range, but for now the asteroid remains partially mysterious even in its discovery.
Where 2025 PN7 came from is another open question. Some asteroids near Earth originate in the main belt between Mars and Jupiter. Others are fragments ejected from the Moon by ancient meteorite impacts. In this case, telescopic data remains too sparse to pinpoint a source. "For now, we can only speculate," de la Fuente Marcos said. The lack of origin data does not diminish the find—it simply means scientists are working with incomplete information, a common state in astronomy.
What researchers do know is that this visitor will not stay forever. Quasi-moons differ from true moons, which orbit a planet directly and typically remain for only months. Earth has hosted several such temporary companions, including 2024 PT5, which arrived last autumn and departed by November. Quasi-moons, by contrast, maintain their solar orbit while remaining synchronized with Earth's path, sometimes for centuries or even millennia. This stability makes them intriguing targets for future space missions. China's Tianwen-2 mission, for instance, plans to visit and collect samples from Kamoʻoalewa, another quasi-moon.
2025 PN7 will not remain in Earth's neighborhood indefinitely. Orbital simulations suggest it will stay within the system for 126 years, departing around 2083. At its closest approach, the asteroid ventures to within 4 million kilometers of Earth—roughly ten times the distance to the Moon. At its farthest, it swings out to 17 million kilometers. The timing of its arrival, coinciding with the space age itself, adds a layer of historical coincidence to the discovery. For six more decades, this tiny rock will continue its silent orbit, a passenger in Earth's cosmic lane, before the gravitational choreography of the solar system eventually ejects it into the void.
Notable Quotes
For now, we can only speculate— Carlos de la Fuente Marcos, Complutense University of Madrid, on the asteroid's origin
The Hearth Conversation Another angle on the story
Why does it matter that we found this particular asteroid now, after it's been here for nearly 70 years?
Because we didn't have the tools or the systematic sky surveys before. Pan-STARRS is relatively new. Once they spotted it, they could look back at old photographs and trace its path. That's how you confirm something is actually in a stable orbit with us, not just passing through.
So we've been sharing space with this rock the whole time and never knew?
Yes. And there are probably others we haven't found yet. The smaller something is, the harder it is to see. A 16-meter asteroid is genuinely tiny against the backdrop of space.
The scientist said they can't even agree on its size—16 meters or 49 meters. How does that happen?
It's all about reflection. You measure how much sunlight bounces back. But if the surface is dark or irregular, or if it's tumbling, the measurements get fuzzy. You need more observations to pin it down.
And nobody knows where it came from?
Not yet. It could be from the asteroid belt, could be a piece of the Moon knocked loose billions of years ago. The data just isn't there. That's honest science—saying what you don't know.
Will it ever hit us?
No. The simulations are clear on that. It stays in its lane, roughly 4 to 17 million kilometers away. It's more like a car in the next lane than a threat. And in 2083, it'll drift out of the system entirely.
Could we use it for something?
That's the interesting question. Quasi-moons are stable enough that missions could reach them. China is already planning to visit Kamoʻoalewa. This one is smaller, harder to reach, but it's there if we ever want to study it up close.