An asteroid about the size of a city bus is about to become a “mini-moon” as it gets caught up in Earth’s gravitational pull. Named 2024 PT5, this asteroid is expected to enter Earth’s orbit on September 29, 2024 and remain until November 25. Although the term “mini-moon” may sound strange, scientists use it to describe any small celestial body that is temporarily captured by Earth’s gravity. The asteroid was discovered by the ATLAS (Asteroid Terrestrial-impact Last Alert System) project back in August.

It’s not a rare occurrence

Mini-moons are not as rare as one might think. These space objects are usually small asteroids that pass close enough to Earth to be captured by gravity, often briefly. 2024 PT5 is expected to remain within Earth’s orbit for just under two months before continuing its journey through space. Similar mini-moons have been recorded in recent years. For example, in 2020, an object thought to be a mini-moon was later identified as space debris from a 1960s rocket launch. However, 2024 PT5 is believed to be a real asteroid, according to ATLAS scientists.

Temporary flyover

Although called a mini-moon, 2024 PT5 will not complete a full orbit around Earth. Instead, it will be a “temporarily captured flyby,” circling about 25 percent of the planet’s surface before heading back into the solar system. These brief encounters are common, and many mini-moons do not stick around long enough to form a stable orbit.

Can you see it?

Unfortunately, spotting this mini-moon with the naked eye or even most telescopes will be nearly impossible. The magnitude or brightness of an asteroid is too faint to be detected by standard amateur astronomical equipment. Its absolute magnitude is reported to be 27.593, much fainter than can be observed even with a 12-inch telescope. Only the most advanced observatories will be able to observe the brief appearance of this mini-moon.