Earth to Get a Temporary Second Moon: When and How to Spot It

Starting September 29, Earth will have a temporary companion in orbit. An asteroid named 2024 PT5 will become a “mini-moon,” orbiting Earth for nearly two months until November 25, according to a study published in Research Notes of the American Astronomical Society. 

Discovered on August 7 by the Asteroid Terrestrial-impact Last Alert System in Sutherland, South Africa, the asteroid belongs to the Arjuna class, which are small bodies with Earth-like orbits.

While mini-moons can orbit Earth for various lengths of time, ranging from a few days to over a year, 2024 PT5's stay will last approximately two months. 

The asteroid will return to orbiting the Sun after its brief period with Earth. Previous mini-moons include short-lived events in 1981 and 2022.

To qualify as a mini-moon, an object must approach Earth within about 2.8 million miles (4.5 million km) and travel at a steady pace of around 2,200 mph (3,540 km/h), according to Carlos de la Fuente Marcos, a professor at Universidad Complutense de Madrid.

Although Earth will technically have two moons during this period, 2024 PT5 will not be visible to the naked eye due to its small size and dim brightness.

According to experts, the asteroid is too faint for typical amateur telescopes and binoculars. However, professional astronomers with telescopes at least 30 inches in diameter, coupled with specialized equipment like CCD or CMOS detectors, should be able to observe it.

For the next two months, while the moon continues to shine brightly, 2024 PT5 will quietly accompany it in Earth’s orbit.