minimoon

A minimoon, also known as a temporary moon or a captured object, is a small celestial body that temporarily orbits a planet, typically Earth, before eventually escaping its gravitational pull or colliding with it. Unlike natural satellites like the Moon, which have stable orbits, minimoons are irregular objects that enter and leave Earth’s gravitational influence over relatively short timescales, often measured in months or years.

The concept of minimoons was first proposed in the 1970s, but the first confirmed observation occurred in 2006 with the discovery of 2006 RH120, a small asteroid estimated to be about 2–3 meters in diameter. This object orbited Earth for nearly a year before departing. Since then, several other minimoons have been identified, including 2020 CD3, which was confirmed in 2018 and remained in orbit until 2020.

Minimoons are believed to originate from the asteroid belt between Mars and Jupiter or, in some cases, from near-Earth objects (NEOs) that come too close to Earth’s gravity. Their temporary capture is thought to result from complex gravitational interactions, where the object’s velocity and trajectory align just right to be pulled into a loose orbit. Unlike stable moons, minimoons follow highly elliptical or chaotic paths, making their orbits unpredictable over long periods.

Studying minimoons provides valuable insights into the dynamics of near-Earth space and the behavior of small celestial bodies. They also offer potential opportunities for future space missions, as their proximity to Earth makes them accessible targets for scientific research or even resource extraction. However, their transient nature means they cannot be relied upon as permanent satellites.

While minimoons are rare, advances in astronomical observation—particularly with telescopes like Pan-STARRS and the Catalina Sky Survey—have increased their detection rates. As technology improves, scientists anticipate discovering more of these fleeting companions, further expanding our understanding of Earth’s dynamic orbital environment.