Earth still has a moon and it will remain that way until Thanksgiving
It sounds like something out of a science fiction movie. In recent weeks, a ‘mini moon’ the size of a city bus has been in Earth’s orbit. The celestial body is more than just a guest staying for a short visit. It’s here to stay, or at least until Thanksgiving week. But it’s not a moon. In fact, it’s an asteroid called 2024 PT5. It entered orbit on September 29 and will remain in our sky until November 25 before returning to the solar system.
Scientists call such phenomena mini-moons. The asteroid was found 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, have been discovered to be random pieces of space junk. The 2020 mini-moon was eventually identified as a rocket booster from the Surveyor 2 Centaur launch in 1966. But ATLAS reports that this new mini-moon is likely a true asteroid, which is simply defined as a small, rocky object floating in a orbits the sun.
Amateur astronomer Tony Dunn posted a simulation on X of what the asteroid’s path will look like. 2024 PT5 has been near Earth since July.
During the event, the asteroid geocentric energy will become negative and remains so for 56.6 days. In Dunn’s simulation, the orbit is shown as the red line, and it only encircles about 25% of the Earth.
The asteroid won’t complete a full orbit around Earth, so some astronomers call it one temporarily captured flyby. Minimoons that complete a total orbit of the Earth are called temporarily captured orbiters.
Don’t expect to see the mini-moon
It is unlikely that you will see the mini-moon. says NASA the absolute magnitude of 2024 PT5 is 27,593. That means it’s quite faint and won’t be visible even if you have 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 with a magnitude of about 16 or 17. That means amateur astronomers will have to sit this out, as you would have a will need a much larger telescope to see PT5 in 2024.
Minimoons are not particularly rare. They occur almost every year. Earth had a mini-moon in 2022 thanks to the special flight path of the 2022 YG asteroid. Another arrived in 2020 thanks to the 2020 CD3 asteroid. Some of them are even bright enough to see with amateur astronomy instruments.
Many asteroids also return again and again for repeat visits. The 2022 NX1 asteroid became a mini-moon 1981 and 2022. The return is scheduled for 2051. One of the best examples is the 2006 RH120, which orbited the Earth for a full year between July 2006 and July 2007. The phenomenon is so consistent that say some researchers that there is always a mini-moon lurking somewhere on Earth.
