Earth Will Be Getting a New Mini-Moon for Two Months, but You’re Probably Not Going to Be Able to See It

At the end of September, humans will be able to say that Earth has two Moons. Unfortunately, the Moon party won’t last forever, and it’s unlikely you’ll be able to see the newest satellite in the sky, either: It’s too small.

Asteroid 2024 PT5. Earth’s new mini-Moon was detected in early August by the NASA-funded Asteroid Terrestrial-impact Last Alert System, also known as ATLAS, although it wasn’t identified as a mini-Moon until recently. Researchers presented their findings about 2024 PTS in a study published in Research Notes of the AAS.

According to the study, 2024 PT5 has been temporarily captured by Earth’s gravity, which means it will soon start to orbit our planet and become a mini-Moon. Researchers say that 2024 PT5 will follow a horseshoe path and become a mini-Moon from Sept. 29 to Nov. 25. The natural object likely came from the Arjuna asteroid belt, a diverse group of asteroids that exhibit Earth-like orbits around the Sun.

Goodnight, mini-Moon. Don’t expect to see a drastic change in the sky just because Earth snatched a secondary (and temporary) Moon. 2024 PT5 is just 33 feet (10 meters) wide. In comparison, the Moon (the big one) has a diameter of 2,159 miles (3,475 km), less than a third of the width of Earth.

“If Earth were the size of a nickel, the Moon would be about as big as a coffee bean,” NASA points out.

What are mini-Moons? Although the prospect of getting a new Moon sounds quite exciting, it’s not that unheard of. Earth regularly captures objects and pulls them into orbit. Sometimes, it even grabs onto space trash. As explained by The Planetary Society, experts have misidentified space trash, including the Gaia spacecraft and the rocket stages from the from the Chang’e 2 and Lunar Prospector missions, as mini-Moons several times.

However, true mini-Moons aren’t man-made objects. They’re asteroids that get caught in Earth’s gravity and temporarily orbit around the planet. Historically, scientists have had a hard time finding mini-Moons because they tend to be small and move very fast.

In fact, not everyone is convinced that 2024 PT5 is a real mini-Moon. According to The New York Times, the asteroid has to orbit the Earth fully at least once to be classified as a mini-Moon. Notably, 2024 PT5 will follow a horseshoe path.

“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,” Lance Benner, a planetary scientist at NASA’s Jet Propulsion Laboratory, told the outlet.

Only four true mini-Moons have ever been identified, the Planetary Society states. The most recent sighting was in 2022.

The importance of mini-Moons. This might seem to be a lot of fuss over an object that’s 33 feet wide, but there’s more to mini-Moons than meets the eye. Scientists believe that asteroids contain precious metals, such as cobalt, iron, and platinum, and minerals that are short supply on Earth. There are already companies lining up to mine them, although no one has managed it so far.

“Every time they’re talking about asteroid mining, they talk about mini-moons,” said Federica Spoto, an asteroid dynamics researcher, as reported by the Times.

A possible return? This might not be the last we see of 2024 PT5. The study’s authors say that it could return in January 2025 and in 2055.

Images | NASA

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