Earth will have a 'mini-moon' for nearly 2 months starting Sunday, researchers say. Here's what that means.
An asteroid will be caught in Earth's gravitational pull starting Sept. 29.
Starting today through Nov. 25, Earth will have a temporary companion — a mini-moon.
Technically, it’s not a real moon but rather a 37-foot asteroid called “2024 PT5” believed to be from the Arjuna asteroid belt that will be caught in Earth’s gravitational pull, according to a study in the journal Research Notes of the American Astronomical Society.
Discovered on Aug. 7 via NASA's Asteroid Terrestrial-impact Last Alert System, 2024 PT5 is following a horseshoe-shaped path. This means it will make a partial orbit around Earth before resuming its normal sun-centered orbit.
So what is a 'mini-moon,' you ask?
It's when small objects in space, like asteroids or pieces of space debris, temporarily get caught in Earth's orbit. Some mini-moons, called temporary captured "orbiters," make a full circle around the planet before moving on, reports CNN. Others, like 2024 PT5, don't make a full rotation and are labeled temporary captured "flybys."
According to Space.com, for an object to become a mini-moon it needs to approach Earth at a distance of roughly 2.8 million miles and move slowly, at a speed of around 2,200 mph.
"Under these conditions, the geocentric energy can become negative, and the object becomes temporarily bound to Earth," Carlos de la Fuente Marcos, co-author of the study and a professor at Universidad Complutense de Madrid, told the outlet.
Where did it come from?
According to Marcos, 2024 PT5 is part of the Arjuna asteroid belt — a secondary belt consisting of space rocks with orbits closely resembling Earth’s — and are an average distance of about 93 million miles from the sun.
There's also another theory to consider. Paul Chodas, director of NASA’s Center for Near-Earth Object Studies, told the New York Times that the object might be a small fragment from our own moon, possibly knocked loose by an unknown impact.
Others, like Lance Benner, the principal investigator of the asteroid radar research program at the Jet Propulsion Laboratory, believes 2024 PT5 might not qualify as a mini-moon at all.
"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," Benner told the New York Times, stressing that to normally qualify, an asteroid must orbit Earth fully at least once.
Have there been other mini-moons?
Yes. Science identified two other "orbiters” in 2006 and 2020 as well as two other “flybys” in 1991 and 2022.
"There are several others unpublished," Marcos told Space.com.
Will I be able to see it?
Unfortunately, no. The 37-foot 2024 PT5 is too small to be visible to the naked eye.
“The object is too small and dim for typical amateur telescopes and binoculars,” Marcis said. “However, the object is well within the brightness range of typical telescopes used by professional astronomers.”
Despite this, Marcos said he and his team plan to conduct spectroscopic and photometric observations of 2024 PT5 to learn more about its nature.
