Astronomers Find Potential Planet-Killer Asteroid Hiding in Sun’s Glare

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. These NEAs are part of an elusive population that lurks inside the orbits of Earth and Venus. One of the asteroids is the largest object that is potentially hazardous to Earth to be discovered in the last eight years. 

Astronomers have spotted three new near-Earth asteroids orbiting in the inner solar system, and one of them is the largest such object discovered in the last eight years. While they’re relatively close to Earth, between here and the planet Venus, these space rocks evaded detection by hiding in the sun’s glare. Two of the space rocks are of little concern, but the other crosses Earth’s orbit. We don’t know how serious the threat is yet, but there’s a possibility it could find itself in the same place as Earth in the future. And that would be very bad for anyone living on Earth at the time.

The only reliable way to spot asteroids kicking around the inner solar system is to time observations during twilight, when the sun’s glare is less intense. There are only two 10-minute windows each day to conduct these sweeps, and observations are limited to a section of sky near the horizon. The international team used the Dark Energy Camera located on the Víctor M. Blanco 4-meter Telescope located in Chile. With this instrument, they were able to spot the three near-Earth asteroids (NEAs), dubbed 2021 LJ4, 2021 PH27, and 2022 AP7.

The first two are of little concern, though astronomers are somewhat interested in 2021 PH27 as it’s currently the closest known asteroid to the sun. Temperatures on the surface would be high enough to melt lead. This rock, as well as 2021 LJ4 won’t pose any danger to Earth, but 2022 AP7 is more concerning. This asteroid, which is almost a mile across (1.5 kilometers), crosses Earth’s orbit.

The Dark Energy Camera in operation.

The National Science Foundation’s NOIRLab says 2022 AP7 is a potential “planet killer.” But the emphasis is on potential. 2022 AP7 is not hurtling toward Earth — it has an elliptical orbit around the sun, and the place it crosses Earth’s orbit is currently on the opposite side of the solar system from our planet. 2022 AP7 has a 1:5 near resonance with Earth, which means it takes five years to complete an orbit of the sun. Over time, it is expected to move closer to Earth, but it should not pose any danger for a century or more. Still, this is an object astronomers want to keep tabs on.

Astronomers currently know of over 1,400 NEAs with the potential to impact Earth in the future — you can see a full list of them on NASA’s Center for Near Earth Object Studies website. Should 2022 AP7 or some other object approach Earth in the future, we might be able to deflect it. NASA’s DART mission recently conducted the first test of planetary defense technology, showing that it’s possible to alter an asteroid’s trajectory with a kinetic impactor. NASA says early results from the mission show that the asteroidal moon Dimophos was even more affected by the vessel’s impact than expected.

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