Earth had a temporary mini-moon for the previous 2 months. Asteroid 2024 PT5 temporarily orbited Earth from September 29. Unfortunately, this temporary mini-moon left its orbit around Earth on Monday, November 25, and its next close approach is set for November 8, 2055, said Space.com.

The asteroid measured approximately 10 meters (33 feet) in diameter, making it relatively small compared to many other asteroids. In comparison to other well-known asteroids like Apophis or Bennu, 2024 PT5 was significantly smaller and less massive, which made it impossible to be visible to the naked eye.

Asteroid 2024 PT5 was discovered on August 7, 2024, by NASA’s Asteroid Terrestrial-impact Last Alert System (ATLAS) from its observatory in Hawaii. The naming convention “2024 PT5” indicated the year of discovery and its sequential designation. This discovery was crucial for planetary defense, as ATLAS monitors potentially hazardous asteroids. ATLAS also discovered the famous comet Tschunishan Atlas which was visible from September 27 to October 24.

Asteroid 2024 Pt5 is a small Apollo-Neo-class asteroid orbited Earth due to Earth’s gravitational pull for two months. The asteroid did not collide with Earth but it temporarily orbited the Earth before it shifted to its normal sun-centered orbit.

What is a mini-moon?

The asteroids that fail to escape the earth’s gravitational pull during a flyby and end up orbiting for a brief period of time are called mini-moons. The asteroid 2024 Pt5 is classified as an Apollo-Neo asteroid by NASA. NEOs, or near-earth objects, are objects that fly by Earth within about 120 million miles (190 million kilometers).

There are around 28000 asteroids that are monitored by NASA’s Asteroid Terrestrial Impact Last Alert System (ATLAS).

Previous mini-moons

Such mini-moons are not only rare but also harder to spot. Only 3 mini-moons have been observed before in history.

• Asteroid 2022 NX1 became The first mini-moon in 1981 and again in 2022.
• The asteroid 2006 RH120 became the second mini-moon. It orbited Earth for an entire year from July 2006 to 2007.
• Out of a surprise in 2020 a random space junk from a rocket booster from the 1966 Surveyor 2 Centaur launch became the third mini-moon.