Earth's New "Mini-Moon": 4 Things To Know

Earth is about to get a new asteroid friend, but not the kind that crashes and causes havoc. It’s more of an “in-laws that overstay their welcome” kind of situation. Here’s what you need to know about a new mini-moon: 

What’s happening? 

Back in August, the Asteroid Terrestrial-impact Last Alert System (ATLAS) program discovered a roughly 10-meter-wide asteroid from the Arjuna asteroid belt that will get close enough to Earth to classify it as a “mini-moon” starting on September 29th. The report published in the American Astronomical Society journal, said asteroid 2024 PT5 will make a horseshoe shaped orbit around our planet over the course of 57 days; ending on November 25th. 

What is a “Mini-Moon"? 

“Mini-moons” can range from asteroids to random pieces of space junk floating around. These near-Earth objects will enter Earth’s gravitational pull and will often complete at least a partial revolution around our planet. Sometimes the object doesn’t even complete a full revolution before exiting and continuing its regular heliocentric trajectories.  While asteroid 2024 PT5 won’t complete a full orbit of Earth, some astronomers may call it a “temporarily captured flyby”. 

Will I be able to see it? 

Short answer: no. 

Long answer: 2024 PT5 won’t be bright enough, even with a typical home telescope.  

NASA classifies how bright celestial objects are by their magnitude. Low numbers, including negatives, are brighter, while higher numbers are fainter. 

2024 PT5 has a magnitude of 27.595. The naked eye can see objects as faint as roughly 6.5 magnitude, and a traditional 12-inch telescope can see things with magnitudes between 16-17. To put it in perspective, the moon sits at –13 magnitude.  

Is this a rare event? 

These phenomena aren’t partially rare as the Earth can capture Near Earth Objects all the time. In 2022, a mini-moon called Asteroid 2022 YG entered the Earth’s orbit. Our planet has had a repeated visitor of 2022 NX1 asteroid who became a mini-moon in both 1981 and 2022. That asteroid won’t be back until 2051 though.  

In fact, this happens so often, some researchers believe Earth always has at least one mini-moon hovering in space.