Earth to have a new minimoon: Asteroid 2024 PT5 joins orbit

Astronomers have reported that Earth will have two natural satellites for nearly two months, from September 29 to November 25. In addition to the Moon, asteroid 2024 PT5, known as a minimoon, will also orbit our planet.

Asteroid 2024 PT5 was discovered on August 7 of this year by the ATLAS (Asteroid Terrestrial-impact Last Alert System), a tool designed to detect potentially dangerous asteroids. The asteroid is about 10 metres in diameter, making it too dim to be seen with the naked eye or amateur telescopes.

"Earth can regularly capture asteroids from Near-Earth Objects (NEOs) and pull them into orbit, creating minimoons," said astronomers Carlos de la Fuente Marcos and Raúl de la Fuente Marcos from the Complutense University of Madrid in "The Research Notes of the AAS." They discovered the properties of asteroid 2024 PT5 during routine monitoring of newly discovered objects.

Damian Jabłeka, deputy director of the Silesian Planetarium, explains that even a small celestial body can be considered a natural satellite if it enters Earth's orbit and remains there for a certain period. Certain conditions must be met for this to be possible. "Sometimes, the combination of distance, direction of flight, and velocity of such a small celestial body causes it to be caught in the gravitational potential of our planet and start orbiting," Jabłeka told PAP.

Prof. Carlos de la Fuente Marcos from the Complutense University of Madrid, quoted by Space.com, explained that to become a minimoon, an approaching body must come within about 4.5 million kilometres (2.8 million miles) of Earth and move "slowly," at a speed of about 3,540 kilometres per hour (2,200 miles per hour).

"It hasn't happened yet that, for example, asteroids start orbiting Earth permanently, because the presence of the Moon and the Sun causes them to fly away into space after a few orbits," noted Damian Jabłeka. He added that the studied and documented celestial bodies that have remained in Earth's orbit for longer are asteroid 2006 RH120, our second moon from July 2006 to 2007, and 2020 CD3, which orbited Earth for three years.

After leaving Earth's orbit, object 2024 PT5 will be closest to Earth on January 9, 2025, at 12:00 PM ET, and return only in 2055.