Earth’s new mini-moon makes its debut

On August 7, NASA-funded UH‘s Asteroid Terrestrial-impact Last Alert Survey (ATLAS) telescope in Sutherland, South Africa, detected an asteroid called 2024 PT5, which is being called ‘Earth’s next ‘mini-moon.'”

The asteroid orbits the Sun in a similar way to Earth. This means it stays about the same distance from the Sun as Earth does and follows a path that looks a lot like Earth’s path around the Sun.

Near-Earth objects (NEOs) that move in horseshoe-shaped paths can come close to our planet at low speeds. During these times, they might experience “mini-moon” events, where their energy relative to Earth becomes negative. This means they can stay close to Earth for hours, days, or even months but won’t fully orbit the planet.

This recently discovered small body, 2024 PT5, follows a horseshoe path and will become a mini-moon in 2024. Earth’s gravitational pull will snag 2024 PT5 between September 29 and November 25.

This capture period will last two months before the asteroid escapes Earth’s gravity, with the following close approach expected in 2055.

While there’s no official definition for a “mini-moon,” 2024 PT5 comes within about one million miles of Earth—four times farther than the Moon. It’s so tiny you can only see it with a powerful telescope. Although it doesn’t behave exactly like a moon, it is one of the few objects temporarily captured by Earth’s gravity. In the future, such objects could provide opportunities for collecting samples or even asteroid mining.

Larry Denneau, an astronomer at the UH Institute for Astronomy and ATLAS co-principal investigator, said, “The discovery of 2024 PT5 by our ATLAS telescopes is an important reminder that there are countless small objects orbiting the Sun, and some of them can temporarily become Earth’s companions.”

“While this object poses no threat to our planet, it showcases the invaluable work our team is doing to vigilantly monitor the skies and detect these objects before they make a close approach.”

Journal Reference:

1. Carlos de la Fuente Marcos and Raúl de la Fuente Marcos. A Two-month Mini-moon: 2024 PT5 Captured by Earth from September to November. Research Notes of the American Astronomical Society. DOI 10.3847/2515-5172/ad781f