Earth's new mini-moon swings by, then ghosts us by late November

No need for farewells, 2024 PT5 may drop in again in 2055

Everybody be on their best behavior: Earth has a visitor. 2024 PT₅ is an asteroid that took up residence in orbit on Sunday to become a "mini-moon."

Alas, even if humanity could clean up our space junk, the asteroid would not be staying with us. It's lingering in the neighborhood until November 25, when the forces of gravity will coax it back into a heliocentric trajectory.

2024 PT₅, which measures about ten meters across, was first spotted by the Asteroid Terrestrial-impact Last Alert System (ATLAS) on August 7 – not an overly reassuring time period for space objects that are about to thread the needle between Earth and the Moon.

In any case, an asteroid of this size would likely explode harmlessly in the upper atmosphere. Not that 2024 PT₅ will be coming close enough, as an amateur astronomer's simulation of its trajectory details.

A paper on the find, published in Research Notes of the American Astronomical Society and titled "A Two-month Mini-moon," describes the object as "following a horseshoe path" and notes that its "geocentric energy will remain negative for 56.6 days due to a temporarily captured flyby."

The researchers observed that it has orbital elements "consistent with those of the Arjunas" – a group of near-Earth objects (NEOs) that have low eccentricity, low inclination, and orbital periods close to one year.

Backyard astronomers hoping to catch a glimpse of 2024 PT₅ will be disappointed, however. Because of its dimness and size, you have no chance of seeing 2024 PT₅ with the naked eye or even a home telescope – you'd need professional grade kit.

Fear not – mini-moons are not as rare an occurrence as readers may think. The paper references 2022 NX₁, for instance, which whizzed around Earth in 1981, 2022, and will be back in 2051. Likewise, researchers predict 2024 PT₅ will also be repeating its visit in 2055. Many more mini-moons go completely unnoticed.

For those hoping for asteroids of the more world-ending variety, we have bad news. Last year, The Register reported how scientists claimed to have mapped out NEO movements up to a millennium from now, and none of them lead to a collision.

The closest we'll get is 1994 PC₁, which is about 1 km across and will have a close encounter with Earth in 2525, but with only a 0.00151 percent chance of passing inside the orbit of the Moon – still a ten times higher risk than any other asteroid in the neighborhood.

But never say never. ®