NASA expert identifies mystery object once thought an asteroid

The jig may be up for an "asteroid" that's expected to get nabbed by Earth's gravity and become a mini moon next month. Instead of a cosmic rock, the newly discovered object appears to be an old rocket from a failed moon-landing mission 54 years ago that's finally making its way back home, according to NASA's leading asteroid expert. Observations should help nail its identity.

"I'm pretty jazzed about this," Paul Chodas told The Associated Press. "It's been a hobby of mine to find one of these and draw such a link, and I've been doing it for decades now."

Chodas speculates that asteroid 2020 SO, as it is formally known, is actually the Centaur upper rocket stage that successfully propelled NASA's Surveyor 2 lander to the moon in 1966 before it was discarded. The lander ended up crashing into the moon after one of its thrusters failed to ignite on the way there. The rocket, meanwhile, swept past the moon and into orbit around the sun as intended junk, never to be seen again — until perhaps now.

This September 20, 1966, photo provided by the San Diego Air and Space Museum shows an Atlas Centaur 7 rocket on the launchpad at Cape Canaveral, Florida.

Convair/General Dynamics Astronautics Atlas Negative Collection/San Diego Air and Space Museum via AP

A telescope in Hawaii last month discovered the mystery object heading our way while doing a search intended to protect our planet from doomsday rocks. The object promptly was added to the International Astronomical Union's Minor Planet Center's tally of asteroids and comets found in our solar system, just 5,000 shy of the 1 million mark.

The object is estimated to be roughly 26 feet based on its brightness. That's in the ballpark of the old Centaur, which would be less than 32 feet long including its engine nozzle and 10 feet in diameter.

What caught Chodas' attention is that its near-circular orbit around the sun is quite similar to Earth's — unusual for an asteroid.

"Flag number one," said Chodas, who is director of the Center for Near-Earth Object Studies at NASA's Jet Propulsion Laboratory in Southern California.

The object is also in the same plane as Earth, not tilted above or below, another red flag. Asteroids usually zip by at odd angles. Lastly, it's approaching Earth at 1,500 mph, slow by asteroid standards.

As the object gets closer, astronomers should be able to better chart its orbit and determine how much it's pushed around by the radiation and thermal effects of sunlight. If it's an old Centaur — essentially a light empty can — it will move differently than a heavy space rock less susceptible to outside forces.

That's how astronomers normally differentiate between asteroids and space junk like abandoned rocket parts, since both appear merely as moving dots in the sky. There likely are dozens of fake asteroids out there, but their motions are too imprecise or jumbled to confirm their artificial identity, said Chodas.

Sometimes it's the other way around.

A mystery object in 1991, for example, was determined by Chodas and others to be a regular asteroid rather than debris, even though its orbit around the sun resembled Earth's.

Asteroid hunter Carrie Nugent of Olin College of Engineering in Needham, Massachusetts, said Chodas' conclusion is "a good one" based on solid evidence. She's the author of the 2017 book "Asteroid Hunters."

"Some more data would be useful so we can know for sure," she said in an email. "Asteroid hunters from around the world will continue to watch this object to get that data. I'm excited to see how this develops!"

Chodas predicts the object will spend about four months circling Earth once it's captured in mid-November, before shooting back out into its own orbit around the sun next March. He doubts the object will slam into Earth — "at least not this time around."