The Earth has simply added its seventh confirmed quasi-lunar moon. It’s 2025 PN7, a small Apollo-type asteroid detected in August solely by its brightness, due to the Hawaiian Pan-STARRS 1 telescope.
After analyzing its trajectory, scientists concluded that the item maintains a 1:1 resonance with the Earth. In different phrases, it orbits the solar concurrently our planet. From a distant perspective, this synchronicity makes it look as if the Earth is accompanied by a tiny asteroid—as if it had a further moon.
Not like the moon, quasi-lunar moons are usually not gravitationally sure to the Earth. They’re ephemeral companions, in cosmological phrases, following their very own path across the solar. Solely at sure occasions do they arrive shut sufficient to seem sure. Within the case of 2025 PN7, its minimal distance is 299,000 kilometers, whereas at its farthest level it might attain 17 million km. For comparability, the moon stays at a median distance of 384,000 km from Earth.
In accordance with the article revealed in Analysis Notes of the AAS, the asteroid has been in a quasi-satellite section since 1965, and is predicted to stay so for 128 years. Some researchers estimate that 2025 PN7 will lastly transfer away in 2083.
Why Does the Earth Have Quasi-Lunar Moons?
Thus far, seven our bodies have been confirmed that seem to accompany the planet in its orbit. Astronomers imagine that extra could also be found sooner or later. Earth is a pure reservoir of quasi-lunars as a result of the Earth’s orbit is just like that of sure close by objects that inhabit the so-called Arjuna group of asteroids, a inhabitants that has solely lately begun to be studied in larger element.
The Arjuna group doesn’t kind a hoop just like the asteroid belt between Mars and Jupiter, however includes a legion of near-Earth rocks that orbit the solar on an analogous path as our planet. Sometimes, a few of these asteroids coincide with our trajectory and, relying on their orbital dynamics, are labeled as quasi-lunar or mini moons.
The quasilunar moon 2025 PN7 sits within the Arjuna asteroid group not removed from Earth.Illustration: WIRED
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