A quasi-moon has been tracking Earth for 60 years.

A quasi-moon has been discovered that has been following Earth for about 60 years and will likely accompany us for another six decades : called 2025 PN7 , it is actually an asteroid almost 19 meters in diameter that has entered into a sort of resonance with Earth's orbit , so much so that it appears to be orbiting our planet even though it technically is not . Its identikit is published in Research Notes of the American Astronomical Society by astronomers at the Pan-STARRS Observatory in Hawaii. Using the Horizons system at NASA's Jet Propulsion Laboratory and the Python tools, researchers spotted the quasi-moon on August 2, 2025 , establishing that it has been in its quasi-orbit for about 60 years and will likely remain there for another 60 years before departing. This is a relatively short time compared to that estimated for other known quasi-moons . In fact, 2025 PN7 is only the latest discovery in chronological order: the first quasi-satellite was identified in 1991 and at the time some even believed that it could be an interstellar probe. "Over thirty years later," explain astronomers at the Pan-Starrs Observatory, "it is now widely accepted that these objects are natural and constitute a secondary asteroid belt that occupies the region in which the Earth-Moon system orbits the Sun, defining the dynamical class of Arjunas ." Arjunas with the most Earth-like orbits can undergo temporary capture as mini-moons of our planet. However, mini-moons are different from quasi-moons like 2025 PN7, because mini-moons temporarily orbit Earth, while quasi-moons only apparently do so. Currently, six other quasi-moons are known: 164207 Cardea (2004 GU9), 469219 Kamo'oalewa (2016 HO3), 277810 (2006 FV35), 2013 LX28, 2014 OL339, and 2023 FW13.