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"Planet killer" asteroid with the potential to collide with Earth found hiding in the glare of the sun

Bullseye! How DART hit an asteroid 7 million miles away
Bullseye! How DART hit an asteroid 7 million miles away 05:09

For a long time, the sun's glare has been hiding a secret — a trio of space rocks with one member that could one day be hazardous to the planet. Of the three asteroids recently discovered by astronomers, two are so massive that they have been described as "planet killers" — and one has the potential of crossing Earth's orbit, according to a new study.

The area between the orbits of Earth and Venus is often hidden by the sun's glare, making it "notoriously challenging" for astronomers to observe what might be lurking in the region, scientists say. But recently, astronomers were able to get around the challenge by conducting surveys during two 10-minute windows at night. 

And what they found was well worth the wait. Hidden behind that glare was a trio of near-Earth asteroids, meaning that gravity has thrust them into orbits that "allow them to enter the Earth's neighborhood," according to NASA's Center for Near Earth Object Studies. 

Twilight observations with the US Department of Energy-fabricated Dark Energy Camera at NOIRLab's Cerro Tololo Inter-American Observatory in Chile have enabled astronomers to spot three near-Earth asteroids (NEAs) hiding in the glare of the Sun.  DOE/FNAL/DECam/CTIO/NOIRLab/NSF/AURA/J. da Silva/Spaceengine

The three asteroids have been named 2021 LJ4, 2021 PH27 and 2022 AP7. The first of the three is small and in an orbit that's safely and "completely interior to Earth's orbit." Only about 25 asteroids with this type of orbit have been discovered to date, astronomers said in a press release, because of the sun. 2021 PH27 is in this category as well, with one distinction — it's much larger. 

2021 PH27 has a diameter between 0.9 and 1.7 kilometers (0.5 to 1 mile) long and is the closest known asteroid to the sun, according to a press release by Noir Lab, making its surface so hot that it can melt lead. There are "likely several more" asteroids of this size and type within the region, researchers said in their study. 

"Our twilight survey is scouring the area within the orbits of Earth and Venus for asteroids," astronomer Scott Sheppard, the lead author of the new study, said. "So far we have found two large near-Earth asteroids that are about 1 kilometer across, a size that we call planet killers." 

The third and final newly-discovered asteroid is 2022 AP7, and unlike its other trio members, it has the power to cause a more powerful punch to the planet. This asteroid is larger than 2021 PH27, with a diameter just under a mile long. It's an Apollo asteroid, meaning that it has an orbit path that could one day force it to come into contact with Earth. 

It's also the largest object potentially hazardous to the planet to be discovered in about eight years, researchers said. 

"Over time, this asteroid will get brighter and brighter in the sky as it starts crossing Earth's orbit closer and closer to where the Earth actually is," Sheppard told The New York Times. "...This is what we call a planet killer. If this one hits the Earth, it would cause planetwide destruction. It would be very bad for life as we know it." 

But planetary scientists Tracy Becker told The Times that such an incident in the "foreseeable future" has "extremely low probability." 

And now, the hunt for more asteroids continues using the Dark Energy Camera (DECam), which uses highly-sensitive and high-performance technology to capture large swaths of space sky. 

"Large areas of sky are required because the inner asteroids are rare, and deep images are needed because asteroids are faint and you are fighting the bright twilight sky near the Sun as well as the distorting effect of Earth's atmosphere," Sheppard said in the press release. "DECam can cover large areas of sky to depths not achievable on smaller telescopes, allowing us to go deeper, cover more sky, and probe the inner Solar System in ways never done before."

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