For six decades, it remained hidden in plain sight: a previously unknown quasi-moon, now designated 2025 PN7, has been subtly sharing Earth's orbital path around the Sun. This fascinating celestial body was recently identified by the Pan-STARRS observatory in Hawaii, a discovery detailed in a paper published in the Research Notes of the American Astronomical Society. The detection prompted researchers to scour archival data, revealing images of 2025 PN7 dating back to 2014.
Analysis of this data suggests that 2025 PN7 has maintained a stable, quasi-orbital relationship with Earth for an impressive 60 years. This companionship is projected to continue for another 60 years before gravitational influences subtly alter its trajectory. The asteroid itself is relatively small, measuring approximately 62 feet (19 meters) in diameter, and maintains a significant distance from Earth, ranging from 2.8 million to 37.2 million miles. It was initially observed in the constellation Piscis Austrinus.
Unlike Earth's true moon, which is gravitationally bound to our planet, quasi-moons are not in direct orbit. Instead, their movement around the Sun is subtly influenced by Earth's gravity, creating the illusion of accompanying our planet on its journey. This makes them more akin to temporary celestial companions than true satellites, highlighting the complexities of orbital mechanics.
The discovery of 2025 PN7 underscores the prevalence of near-Earth asteroids and the ongoing need for meticulous celestial observation. This contrasts with so-called 'mini-moons', which are temporarily captured by Earth's gravity for shorter periods, typically lasting weeks or months. The most famous quasi-moon, Kamoʻoalewa (2016 HO3), is currently the target of China's Tianwen-2 mission, aiming to collect samples and deepen our understanding of the solar system's origins. The discovery of 2025 PN7 further expands our knowledge of these fascinating celestial phenomena and the intricate dance of gravitational forces within our solar system.
---
Originally published at: https://gizmodo.com/earths-new-quasi-moon-has-been-hiding-in-plain-sight-for-60-years-2000656143
