There's an asteroid following Earth, and it may be from the moon

This isn't a normal asteroid.

Planetary scientists suspect that a space rock that appears to follow Earth around the sun (because it has a very similar orbit) is likely a chunk of the moon. Importantly, the 150 to 190-foot-wide asteroid is not a threat to Earth, but it's certainly a curiosity in our solar system's neighborhood.

In the new research, published in the science journal Communications Earth and Environment, scientists found the asteroid (named Kamo`oalewa) reflected sunlight much differently than typical asteroids. Rather, it reflected light more akin to lunar rocks.

Indeed, the moon origin seemed unlikely. "We doubted ourselves to death," Vishnu Reddy, an associate professor of lunar and planetary sciences at the University of Arizona and a coauthor of the research, said in a statement.

But after a few years of observations with powerful telescopes, and new observations in 2021, the moon became the best explanation. "It's easier to explain with the moon than other ideas," said Ben Sharkey, a study co-author and University of Arizona planetary sciences graduate student.

Astronomers discovered Kamo`oalewa in 2016 and created a visualization of its orbit, which you can watch below. As it orbits the sun, the asteroid loops around Earth each year, which is why it's been dubbed "Earth's constant companion." This companion, fortunately, doesn't come closer than within 9 million miles of Earth. That's about 38 times farther than the moon.

Importantly, near Earth objects of Kamo`oalewa's size can potentially pose a threat to Earth. Some 50,000 years ago, an asteroid 100 to 170 feet across left a 600-foot-deep crater in Arizona. "A similar-size impact event today could destroy a city the size of Kansas City," David Kring, an impact expert at the Lunar and Planetary Institute, told NASA in 2021.

In a couple weeks, NASA will launch an unprecedented mission to another asteroid, called Dimorphos, to test humanity's ability to deflect an asteroid that's destined to impact Earth. NASA has never, however, issued a warning for an imminent asteroid strike.