Soon, Earth will have two moons. Well, technically, one of them is an asteroid. But that’s nothing to worry about. It won’t hit us, but it will stick around as if it’s part of our orbit for a few months, from early fall through Thanksgiving. The chunk of rock, called 2024 PT5, will fly into Earth’s orbit, get stuck there from September 29 to November 25, and then happily head out into the solar system. Scientists call such phenomena mini-moons.
The asteroid was discovered by a group called ATLASwhich stands for Asteroid Terrestrial-impact Last Alert System, in August. The researchers who found it published a non-peer-reviewed study about the asteroid.
Some past mini-moons, like this one from 2020, turned out to be random bits of space junk. The 2020 mini-moon was eventually identified as a rocket booster from the 1966 Surveyor 2 Centaur launch. But ATLAS reports that this upcoming mini-moon is likely a true asteroid, which is simply defined as a small, rocky object orbiting the sun.
Amateur astronomer Tony Dunn posted a simulation on X what the path of the asteroid will look like. 2024 PT5 has been near Earth since July.
During the event the asteroid geocentric energy will become negative and remain so for 56.6 days. In Dunn’s simulation, the orbit is shown as the red line, and it circles only about 25% of the Earth.
The asteroid will not complete a full orbit around Earth, so some astronomers are calling it a temporarily captured flybyMini-moons that complete a full orbit around Earth are called temporarily captured orbiters.
Don’t expect to see the mini moon
The chances of seeing the mini moon are slim. NASA says The absolute magnitude of 2024 PT5 is 27,593. This means that it is very faint and will not be visible even with a telescope. For referenceThe faintest magnitude visible to the naked eye at night is about 6.5, and a 12-inch telescope can see objects at magnitudes of about 16 or 17. That means amateur astronomers will have to wait this time around, as you’ll need a much larger telescope to see 2024 PT5.
Mini-moons aren’t particularly rare. We see them almost every year. Earth had a mini-moon in 2022 thanks to the unusual flight path of the 2022 YG asteroid. Another appeared in 2020 thanks to the 2020 CD3 asteroid. Some are even bright enough to be seen with amateur astronomical instruments.
Many asteroids also return for repeat visits. The 2022 NX1 asteroid became a mini-moon in 1981 and 2022. The return is planned for 2051. One of the best examples is 2006 RH120, which orbited the Earth for a full year between July 2006 and July 2007The phenomenon is so consistent that some researchers claim that there is always a mini-moon hanging around somewhere on Earth.
