A new mini-moon enters our orbit

Earth has captured a new mini-moon that will orbit our planet for a few months before heading back out on its cosmic journey through the solar system.

The big picture: Scientists think our planet likely has some kind of "mini-moon" in orbit at any given time.

Details: This mini-moon likely isn't an asteroid or any kind of natural detritus. NASA scientists think the mini-moon is actually the spent upper stage of a rocket that boosted the failed Surveyor 2 toward the Moon in 1966.

• The object — named 2020 SO — entered into the part of space where Earth's gravity is dominant on Nov. 8 and is expected to stay there until it heads out to a new orbit around the Sun in March 2021.
• Scientists figured out that the mini-moon is likely a rocket body by observing it and piecing together its past orbits.
• "One of the possible paths for 2020 SO brought the object very close to Earth and the Moon in late September 1966," NASA's Paul Chodas said in a statement. "It was like a eureka moment when a quick check of launch dates for lunar missions showed a match with the Surveyor 2 mission."

Between the lines: Earth's adoption of this mini-moon illustrates how profoundly humanity has changed the space environment.

• Even objects like this one from the earliest days of NASA are still floating around as space junk, possibly threatening operational satellites and spacecraft today.
• NASA estimates there are millions of pieces of space junk in orbit today, and it's just getting more crowded up there as new satellites launch each month.