Astronomers have confirmed the discovery of Earth’s seventh quasilunar moon, named 2025 PN7. This small Apollo-type asteroid, detected in August using the Hawaiian Pan-STARRS 1 telescope, exhibits a unique orbital relationship with our planet. Scientists determined that it maintains a 1:1 resonance with Earth, meaning it orbits the sun simultaneously alongside our planet. This synchronicity creates the illusion of an additional moon from a distance.
Quasilunar moons are not gravitationally bound to Earth like the natural moon. Instead, they serve as transient companions, following their own paths around the sun. 2025 PN7 comes closest to Earth at a distance of 299,000 km, but can be as far as 17 million km away. For context, the average distance from Earth to its moon is approximately 384,000 km.
According to a recent article published in Research Notes of the AAS, 2025 PN7 has been in its quasi-satellite phase since 1965 and is expected to remain in this configuration for another 128 years. Researchers anticipate that the asteroid will finally drift away around 2083. So far, astronomers have identified seven bodies accompanying Earth in its orbit, with hopes that more will be discovered in the future.
Earth acts as a natural reservoir for quasilunar moons due to its orbit being similar to certain nearby objects within the Arjuna group of asteroids. This group includes a range of near-Earth rocks that travel along paths similar to our planet’s orbit. Occasionally, some of these asteroids align with Earth’s trajectory, leading to their classification as quasilunar moons or “mini-moons.” The primary distinction lies in their orbits; quasilunar moons travel with Earth, while mini-moons exhibit a horseshoe-shaped orbital motion around the planet and are typically visible for only a few weeks or months.
The seven known quasilunar moons belong to the Arjuna group and share the same 1:1 resonance with Earth’s orbit. These include 164207 Cardea, 277810, 2013 LX28, 2014 OL339, 469219 Kamoʻoalewa, 2023 FW13, and the newly confirmed 2025 PN7.
The Pan-STARRS observatory has established itself as a leader in the detection of near-Earth objects. Its groundbreaking findings include not only quasilunar moons but also comets and supernovae, facilitated by its advanced 1.4 billion pixel digital camera, the largest of its kind in the world.
In the realm of astronomy, moons can form through different processes. Some planets, like Jupiter and Saturn, capture celestial bodies orbiting nearby. Others, including Earth, form their satellites from collisions that occurred in the early solar system. A crucial factor in defining a true moon is its permanent gravitational bond with its planet. Quasilunar moons, while appearing moon-like, do not meet this criterion and instead follow their own independent orbits around the sun.
The discovery of 2025 PN7 adds to our understanding of the complex dynamics of celestial bodies within our solar system and highlights the ongoing potential for future discoveries in the field of astronomy.
