Earth will Get a Second Moon Temporarily This Month—But It Won’t Stay Long

This month, Earth will briefly gain a second moon in the form of a small asteroid known as 2024 PT5. Unlike our permanent moon, which has been orbiting Earth for about 4 billion years, this "mini-moon" will only stick around for two months before it continues its journey through space. The arrival of 2024 PT5 is a rare but fascinating event, one that excites scientists who study such short-term celestial visitors.

The asteroid 2024 PT5 comes from a group of objects known as the Arjuna asteroids. These small space rocks follow orbits similar to Earth's, at an average distance of around 93 million miles (150 million kilometers) from the Sun. These near-Earth objects occasionally drift close enough to our planet to be temporarily captured by Earth's gravity, and 2024 PT5 is no exception. When this asteroid reaches about 2.8 million miles (4.5 million kilometers) from Earth, it will be pulled into our planet's gravitational embrace, becoming a temporary moon.

However, this mini-moon won't behave like Earth's main satellite. According to Carlos de la Fuente Marcos, a professor at the Universidad Complutense de Madrid and an expert on mini-moon events, 2024 PT5 will not complete a full orbit around Earth. Instead, it will act more like a "window shopper," hovering near Earth for a brief period before being pulled away by the gravitational influence of the Sun.

There are two types of mini-moon events: long-term captures, where the object orbits Earth for a year or more, and short-term events like 2024 PT5’s visit, which last only weeks or months. Long-term captures are much rarer, occurring once every decade or two, while short-term events happen more frequently, with several occurring each decade. The short-term episodes don’t allow the asteroid to fully orbit Earth, and in this case, 2024 PT5 will only linger for about two months.

Mini-moons like 2024 PT5 are pulled out of Earth's orbit by the Sun's gravity, ending their brief stint as Earth's companion. Once 2024 PT5 is ejected, it will return to its original orbit around the Sun as part of the Arjuna asteroid belt.

While the arrival of a second moon sounds thrilling, 2024 PT5 won't be visible to most skywatchers. Its small size and dimness make it invisible to amateur telescopes or binoculars. According to Professor Marcos, only professional astronomers using large telescopes with advanced detectors will be able to observe the mini-moon.

Despite its fleeting presence, scientists are eager to study 2024 PT5. Spectroscopic and photometric observations are planned to better understand the asteroid's composition and behavior during its brief stay. Although temporary, these mini-moons provide valuable opportunities for researchers to study near-Earth objects and how they interact with our planet’s gravitational field.

So, while Earth briefly gains a second moon this month, don't expect to see it with the naked eye. Still, this tiny visitor serves as a reminder of the dynamic and ever-changing nature of our solar system.