Well, it’s time to say goodbye. Not to anyone in particular — just to the minimoon that has been orbiting our Earth for nearly a year. And if you’re asking, “What the hell is a minimoon?” Well, we figured it out and have it all laid out here.
The minimoon is, actually, not a moon at all. It’s an old rocket booster from the 1960s has been orbiting the Earth since late last summer after having an extended exhibition around space. But because it’s been in orbit, it’s not just a piece of space junk—it’s technically a minimoon, which is exactly what it sounds like: a small piece of space debris that orbits a planet. If it sounds very human to love a piece of space garbage we created because it revolves around us, it’s because it is. Cool, right?
Surveyor 2, an unmanned mission to deposit a robotic lunar lander on the moon to explore its surface, took off from Cape Canaveral on September 20, 1966. Unfortunately, a vernier thruster meant to execute a course correction maneuver failed, and the spacecraft tumbled for 54 hours before crashing onto the surface of the Earth’s only natural satellite. The spacecraft’s Centaur model rocket booster, however, continued on its original course. It ended up in a solar orbit for decades before it was recently drawn back into the Earth’s orbit, where it became the minimoon we know and love today.
2020 SD was spotted on telescopes last September and seen coming close to Earth in December. It went around the planet and took a long, elliptical path past the moon’s orbit before coming back around on its current trajectory.
The idea of a relic from the early space age coming back to the planet it launched from is almost romantic, but don’t get too attached. 2020 SO, as it’s known to astronomers, is making its final closest approach to Earth today. It will come within 140,000 miles of Earth, about half-way between the planet and its (permanent, large) moon. This close pass will allow it to pick up energy from the gravitational slingshot effect to escape Earth’s gravity and return to a solar orbit.
The minimoon is too small to be seen with the naked eye, but it can be spotted with a telescope. You can watch a live video feed from the Virtual Telescope Project’s robotic telescopes starting at 6:00 p.m. ET on February 2nd, 2021.
Unlike other astronomical phenomena that tend to reoccur—even if hundreds of years into the future—this is truly your last chance to see this special piece of space junk, a relic from another era of human space exploration, as it heads into further reaches of outer space for good.