Earth to Host Mini-Moon 2024 PT5 for Two Months This Fall

Asteroid 2024 PT5 will orbit Earth as a temporary mini-moon from Sept 29 to Nov 25, with no collision risk. Learn about its discovery, characteristics, and future returns.

Discovery and Key Details

A recently discovered asteroid, designated 2024 PT5, is set to become a temporary mini-moon of Earth, orbiting our planet from September 29 to November 25. After this 56.6-day engagement, it will return to a heliocentric orbit around the Sun. The findings were published in the latest edition of the Research Notes of the American Astronomical Society.

Astronomers first spotted the asteroid on August 7 using NASA-funded ATLAS observatory in South Africa. Lead author Carlos de la Fuente Marcos, from Complutense University of Madrid, estimates the asteroid's diameter at about 37 feet (11 meters), though further measurements place it between 16 and 138 feet (5 to 42 meters) — potentially larger than the Chelyabinsk meteor that exploded over Russia in 2013. Despite its size, 2024 PT5 poses no impact threat, staying at a safe distance of roughly 2.6 million miles (4.2 million kilometers) — about ten times the Earth-Moon distance.

Understanding Mini-Moons

Mini-moons fall into two categories, explains de la Fuente Marcos. Long-term captures, known as temporarily captured orbiters, complete multiple revolutions over years. Short-term captures, like 2024 PT5, are called temporarily captured flybys and only orbit for days to months. Earth previously hosted a long-term mini-moon, Asteroid 2020 CD3, which circled for a few years before detection. Short-term events can occur several times per decade, while long-term events are rarer, happening once every 10 to 20 years.

Conditions for Capture

For an asteroid to become a mini-moon, it must approach Earth slowly and at close range. The required conditions: approach within 2.8 million miles (4.5 million kilometers) of Earth at speeds under 2,237 miles per hour (3,600 kilometers per hour). Robert Jedicke, a solar system specialist at the University of Hawaii’s Institute for Astronomy, notes that almost all asteroids approach too fast or at the wrong angle to be captured. Only occasional gravitational nudges from solar system objects allow a slow-moving, correctly angled asteroid to be temporarily captured.

Origin and Future Observations

Asteroid 2024 PT5 likely originates from the Arjuna asteroid group, whose members share Earth-like orbits. Researchers plan to gather more data using advanced telescopes like the Gran Telescopio Canarias and Two-Meter Twin Telescope in Spain’s Canary Islands. However, the asteroid will be too faint for amateur telescopes or binoculars. After its mini-moon phase, 2024 PT5 will make a close approach on January 9, 2025, and may return as a mini-moon in November 2055 and early 2084, offering scientists repeated opportunities to study these intriguing celestial objects.