For a brief moment, Earth’s moon had some company in its lonely existence, in the form a space rock temporarily caught in Earth's orbit. Although it wasn't discovered by astronomers until February 2020, the mini-moon (most likely a small asteroid) had already been gravitationally bound to Earth for several years.
Astronomers gave the “temporarily captured object” the designation 2020 CD3. The so-called mini-moon, about the size of a small automobile, was only the second temporary moon that scientists had ever observed. 2006 RH130 visited in 2006 and 2007 before leaving for parts unknown.
And 2020 CD3 has already gone the same way. Scientists believe that it broke free of Earth's gravitational pull in March and is currently on its way to enter the Sun's orbit.
So long, mini-moon:
- The recently departed 2020 CD3 circled Earth about once every 47 days in a wide, oval-shaped orbit.
- Astronomers say that a new object -- which they're calling 2020 SO -- is headed into our orbit soon, and is expected to hang around until May 2021.
- Unlike the other two mini-moons, 2020 SO is classified as an Apollo asteroid, a class of bodies familiar with Earth’s orbit. Scientists say its characteristics are consistent with something made by humans, probably a hunk of space junk.