In the cosmic ballet of asteroids passing by Earth, most go unnoticed as they zip past. Occasionally, one makes a fiery entrance by crashing into our atmosphere. But every so often, a space rock gets caught in Earth’s gravity, circling the planet temporarily like a fleeting second moon. This rare event is about to happen again.

A recently spotted asteroid, named 2024 PT5, is set to briefly join Earth’s orbit, making it a temporary companion from September 29 to November 25. Discovered on August 7 using the NASA-funded Asteroid Terrestrial-impact Last Alert System (ATLAS), this small asteroid, just 33 feet long, will loop around the planet before continuing its journey through space.

“It is pretty cool,” said Federica Spoto, an asteroid dynamics researcher at the Center for Astrophysics, Harvard & Smithsonian, who was not involved with the study. She added that observing 2024 PT5 will help scientists better understand asteroids that come close to Earth—some of which occasionally collide with it.

What is Mini Moon?

These temporary satellites, known as mini moons, are hard to spot due to their small size and fast speed. Often, they’re mistaken for human-made space debris, such as leftover rocket parts. But in the case of 2024 PT5, astronomers are confident it’s a natural object. “Every time an object with an orbit so Earth-like is discovered, there is a chance that we are just recovering space debris,” said Raúl de la Fuente Marcos, an astronomer at Complutense University of Madrid and co-author of the study. But, he said, observations of 2024 PT5 indicate that “it is a natural object, no doubt about that.”

Adding an intriguing twist, astronomers believe the asteroid may not be just any space rock. According to Paul Chodas, the director of the Center for Near Earth Object Studies at NASA’s Jet Propulsion Laboratory, 2024 PT5 might be a fragment of the moon itself, possibly ejected by a past lunar impact.

Despite its possible lunar origins, some scientists are debating whether it truly qualifies as a mini moon. For an asteroid to earn that title, it must complete at least one full orbit of Earth. 2024 PT5, however, will follow a horseshoe-shaped trajectory, which means it won’t finish a complete revolution around Earth. “It certainly won’t complete one full revolution in the Earth-moon system this fall, so I’m not sure I would classify it as a mini moon,” said Lance Benner, principal investigator of the asteroid radar research program at NASA’s Jet Propulsion Laboratory.

Armageddon Can become Reality?

Beyond the cool factor of having a temporary space companion, asteroids like 2024 PT5 could offer future opportunities. Some contain valuable metals, sparking dreams of asteroid mining. “Every time they’re talking about asteroid mining, they talk about mini moons,” Dr. Spoto said. Future missions could even nudge a metal-rich asteroid into orbit, turning it into a prospecting target for companies eager to harvest resources from space.

Astronomers are also keen to study objects like 2024 PT5 for planetary defense. While the biggest threat comes from near-Earth objects large enough to destroy cities—roughly 460 feet across—there are millions of smaller, yet still dangerous, asteroids capable of causing widespread damage. Researchers have identified about 11,000 of the estimated 25,000 large asteroids near Earth, but far more remain unknown.

As the asteroid prepares to make its close approach, 2024 PT5 serves as a reminder of the bustling “highway” of space rocks whizzing by Earth. Understanding the nature and paths of these objects is crucial, Dr. Spoto noted: “There’s a pretty busy highway around the Earth... Knowing where all of the traffic is going, and what it’s like, is of paramount importance to all seven billion of us.”