• An object called 2020 SO is about to briefly become a "mini-moon," captured by Earth's orbit.
  • There's a chance, however, that the object in question may actually be a piece of space junk leftover from a mission that launched more than 50 years ago.
  • This isn't the first time Earth has captured a mini-moon, nor is it the first time we've mistaken space junk for an asteroid.

A strange object is hurtling toward Earth and, according to estimations of its trajectory, it will briefly become a mini-moon.

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Earth has captured mini-moons before, so this new one, 2020 SO, wouldn't be the first of our moon's tiny companions. But there's something strange about it: Astronomers believe the object may actually be a piece of human-made space junk that's, well, returning home.

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Some scientists think the object may be what's left of a mission that launched for the moon more than 50 years ago. NASA's Surveyor 2 spacecraft launched atop an Atlas LV-3C Centaur-D on September 20, 1966. Unfortunately, NASA lost contact with the craft three days later when a thruster failed to start, sending the mission on a tailspin into the lunar surface.

The working theory is that 2020 SO may actually be the Centaur stage of the United Launch Alliance rocket that propelled Surveyor 2 out of Earth's orbit. The object's size, which researchers have determined to be roughly between 21 and 46 feet long, is a relatively close match for the rocket's dimensions (approximately 41 feet). It's also moving at a much slower clip than what is expected of a natural asteroid, or even rocks that have been ejected from the lunar surface.

"I suspect this newly discovered object 2020 SO to be an old rocket booster because it is following an orbit about the Sun that is extremely similar to Earth's, nearly circular, in the same plane, and only slightly farther away the Sun at its farthest point," Paul Chodas, the director of NASA's Center for Near Earth Object Studies, told CNN. He continued:

"That's precisely the kind of orbit that a rocket stage separated from a lunar mission would follow, once it passes by the Moon and escapes into orbit about the Sun. It's unlikely that an asteroid could have evolved into an orbit like this, but not impossible."
nasa's surveyor 2 mission, which launched on september 20, 1966, and crashed into the lunar surface two days later
NASA
NASA’s Surveyor 2 mission, which launched on September 20, 1966, and crashed into the lunar surface three days later.

Typically, when a rocket launches, any attached boosters fall back down to Earth and are either recovered or crash into the ground (hopefully not in a crowded area). Once the first stage runs out of fuel, it detaches and often burns up in Earth's atmosphere. And once any lingering stages used to propel a spacecraft have been spent, they're discarded in Earth's orbit or drift off and eventually join a heliocentric orbit.

"You have to keep tracking these things, or you can just sort of lose sight of them really easily," Alice Gorman, a space archaeologist at Flinders University in Australia, told ScienceAlert. "And if they do something a little bit unpredictable, and you look the wrong way, then you don't know where it's gone. It is quite astonishing, the number of things that have gone missing."

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Of course, this isn't even the first time we've been tricked by an old launch vehicle. Spent rocket stages have duped us before: In 2002, an amateur astronomer spotted an asteroid that was later named J002E3. Further analysis revealed that the "asteroid" in question was actually the upper S-IVB stage of Apollo 12's Saturn V, which had launched for the moon in 1969.

Researchers hope to get a closer look at 2020 SO on December 1, when it will swing within 31,000 miles of Earth, and in February 2021, when it will swing past Earth again, this time at a distance of approximately 137,000 miles.

It looks like 2020 SO will enter and exit Earth's orbit via the Lagrange points, which are a set of gravitationally stable points between Earth and the sun. It's expected to kiss our Earthly orbit goodbye next May. (Take us with you, rocket.)


🔭The Best Telescopes for Stargazing

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Gskyer AZ Astronomical Refractor Telescope
Gskyer AZ Astronomical Refractor Telescope
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With more than 19,000 reviews on Amazon and a 4.4/5 rating, it's not hard to see why the Gskyer telescope is a fan favorite. This option features a 70mm aperture and fully coated optimal lenses to offer a crisp, clear view of the night's sky. Tech savvy stargazers will appreciate wireless remote, smart phone adapter, and the additional Barlow lens that triples the magnification of each eye piece. Thanks to its adjustable, aluminum alloy tripod, this telescope is suitable for every member of the family.

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If you're looking for a telescope for kids, or if you're a beginner, this HEXEUM model is a high-quality choice. It comes with an 70mm aperture, plus two eyepieces at 10mm and 25mm each. You'll particularly love that this telescope comes with a phone adapter, which means you can attach your phone to the eyepiece and finally get an amazing photo of the night sky.

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ECOOPRO 70mm Astronomy Refractor Telescope
ECOOPRO 70mm Astronomy Refractor Telescope

Easy to set up and compact, this telescope comes with a 70mm aperture, two eye pieces, a finder scope, and a tripod. Perfect for astrology or even bird watching, you can set it up on a tabletop with the tripod set to 15 inches, or extend the legs as long as 47 inches. It also comes with a map of the moon and stars for easy reference.

ESSLNB Kids' Telescope
ESSLNB ESSLNB Kids' Telescope
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ESSLNB's telescope is a great choice for kids or beginners. It features a built-in reversing lens, which means that none of the images you see will ever be upside down. Its 70mm lens gives you a wide range of vision, and the telescope's brightness makes everything easy to see. Plus, you can connect your phone and finally take a decent picture of the night sky.

Beginner stargazers will find a lot to love about Emarth's Telescope. Using it is easy: All you need to do is point the tube in the direction of the desired object and take a gander. With two high-quality eyepieces (70mm and 360mm) that provide low- and high-power views of celestial objects, you'll be able to satisfy your stargazing wishes with ease.

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NASA Lunar Telescope for Kids
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Consider NASA Lunar Telescope the perfect option for avid adventurers or kids who are yearning to spontaneously stargaze. Clocking in at a little over two pounds, this option is lightweight enough to stow in the trunk of your car. This telescope features a multi-coated, extra-low dispersion optical glass to ensure you'll score a clear, perfectly contrasted view of the night's sky.

Celestron 70mm Refractor Telescope
Celestron 70mm Refractor Telescope

Great for beginners (and priced accordingly), this option features a wide, 70 millimeter aperture that will make stars and constellations appear bright and clear. With two eyepieces—10mm to 20mm—it's suitable for a range of stargazing experiences. Download the SkyPortal app to help you find specific sites, or use Celestron's Starry Night software—both are free. To top it off, the telescope comes with a tripod, a finder scope, and a backpack to carry it all.


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Jennifer Leman

Jennifer Leman is a science journalist and senior features editor at Popular Mechanics, Runner's World, and Bicycling. A graduate of the Science Communication Program at UC Santa Cruz, her work has appeared in The Atlantic, Scientific American, Science News and Nature. Her favorite stories illuminate Earth's many wonders and hazards.