Earth Gains a Temporary Second Moon

For a brief period this fall, Earth will be accompanied by a second “mini-moon” as an asteroid, designated 2024 PT5, enters our planet’s gravitational orbit. This celestial visitor will remain with Earth from September 29 through November 25 before escaping its temporary orbit.

Astronomers believe that 2024 PT5, though only about 10 meters in diameter, will act as a mini-moon during its short stay. Unfortunately, due to its small size, it won’t be visible to the naked eye. NASA discovered the asteroid on August 7, and experts suspect it came from the Arjuna asteroid belt. Once it exits Earth’s orbit, the mini-moon will return to its origin in space.

According to researchers Carlos and Raúl de la Fuente Marcos, Earth occasionally captures asteroids from the Near-Earth Object (NEO) population, pulling them temporarily into its gravitational field. These objects, known as mini-moons, often come and go without completing a full orbit around the planet.

NASA defines a near-Earth object as any celestial body drawn toward Earth by the gravitational pull of nearby planets. NASA’s dedicated program monitors and tracks over 28,000 asteroids, providing detailed data about their orbits and potential close approaches to Earth.

Paul Chodas, director of NASA’s Center for Near Earth Object Studies, speculates that 2024 PT5 may even be a fragment of our moon, possibly ejected from a previous impact. While this mini-moon will briefly stay with Earth, it joins a larger category of temporarily captured flybys—asteroids that don’t complete full orbits and quickly move on. Others, known as temporarily captured orbiters, can remain with Earth for much longer, sometimes even years.

For the next two months, Earth’s skies will feature this fascinating, albeit nearly invisible, cosmic companion before it returns to its journey through the solar system.