Earth is temporarily getting a second moon! Here’s everything you need to know.

An asteroid about the size of a city bus will soon become a “mini-moon” as it becomes trapped in Earth’s gravity. The asteroid, named 2024 PT5, is expected to enter Earth’s orbit on September 29, 2024, and remain there until November 25. Although the term “mini-moon” sounds strange, scientists use it to describe any small celestial body that is temporarily captured by Earth’s gravity. The asteroid was discovered in August by the Asteroid Terrestrial-impact Last Alert System (ATLAS) project.

Not a rare event

Mini-moons aren’t as rare as you might think. These space objects are typically small asteroids that pass close enough to Earth to be captured by its gravity, often for short periods of time. 2024 PT5 is expected to remain in Earth’s orbit for less than two months before continuing its journey through space. Similar mini-moons have been recorded in recent years. 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 scientists at ATLAS.

A temporary flyby

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

Can you see it?

Unfortunately, it will be nearly impossible to spot this mini-moon with the naked eye or even with most telescopes. The magnitude, or brightness, of the asteroid is far too faint to be detected by standard amateur astronomy equipment. The absolute magnitude is reported 27,593, much fainter than what can be seen with even a 12-inch telescope. Only the most advanced observatories will be able to follow the brief appearance of this mini-moon.