Earth's Little Second Moons
Every so often, the Earth catches a tiny asteroid and keeps it for a while as a second moon.
What was reported
In 2006, the Catalina Sky Survey in Arizona found a few-metre-wide asteroid, 2006 RH120, circling the Earth. It stayed for about a year before drifting off. Another, 2020 CD3, was found in 2020.
In August 2024, a telescope at Sutherland in South Africa picked up 2024 PT5, a rock about ten metres across that was briefly caught by Earth's gravity that autumn. Newspapers around the world reported that the Earth had a second moon.
Explanations offered
These are small near-Earth asteroids moving at almost the same speed as the Earth around the Sun, so Earth's gravity can pull them into a loose, temporary orbit for weeks or months. Astronomers think there is usually at least one around, too small and faint to be seen.
- When
- 2006, 2020 and 2024
- Where
- In orbit, spotted from Sutherland, South Africa
- Witnesses
- Sky surveys in the United States and South Africa
- Status
- Confirmed
Famous cases are real, widely reported events. Each file sets out what witnesses said and the explanations that have been offered, without taking a side.