A “Planet killer” asteroid that has been hiding in the sun’s glare has finally been observed, and the massive space rock could smash into Earth one day.
The 0.9-mile-wide (1.5-kilometer-wide) “potentially hazardous” asteroid 2022 AP7 is one of several large space rocks discovered recently near the orbits of Earth and Venus.
Currently, 2022 AP7 crosses Earth’s orbit while our planet is on the opposite side of the Sun, but scientists believe that over thousands of years, the asteroid and Earth will gradually begin to cross the same point closer together, increasing the chances of a catastrophic collision. The asteroid, discovered alongside two other near-Earth asteroids at Chile’s Cerro Tololo Inter-American Observatory, was described in a study published in The Astronomical Journal on September 29.
“So far we have found two large near-Earth asteroids [NEAs] that are about 1 km [0.6 mile] across, a size that we call planet killers,” lead study author Scott Sheppard, an astronomer at the Carnegie Institution for Science in Washington, D.C., said in a statement. “Planet killer” asteroids are space rocks that are big enough to cause a global mass extinction event if they were to smash into Earth.
The astronomers used the Cerro Tololo Victor M. Blanco 4-meter Telescope’s Dark Energy Camera to search for asteroids in the inner solar system. Because the sun’s glare makes observations impossible for most of the day, the researchers only had two 10-minute windows of twilight each night to make their observations.
“Only about 25 asteroids with orbits completely within Earth’s orbit have been discovered to date because of the difficulty of observing near the glare of the Sun,” Sheppard said. “There are likely only a few NEAs with similar sizes left to find, and these large undiscovered asteroids likely have orbits that keep them interior to the orbits of Earth and Venus most of the time.”
NASA monitors the locations and orbits of approximately 28,000 asteroids using the Asteroid Terrestrial-impact Last Alert System (ATLAS), a network of four telescopes capable of scanning the entire night sky every 24 hours. Any space object that comes within 120 million miles (193 million km) of Earth is classified as a “near-Earth object,” and any large body that comes within 4.65 million miles (7.5 million km) of our planet is classified as “potentially hazardous.”
Since its launch in 2017, ATLAS has detected over 700 near-Earth asteroids and 66 comets. ATLAS detected two asteroids, 2019 MO and 2018 LA, which both collided with Earth, the former exploding off the southern coast of Puerto Rico and the latter crashing near the border of Botswana and South Africa. Fortunately, the asteroids were small and did not cause damage.
NASA has calculated the trajectories of all near-Earth objects out to the end of the century. According to NASA, there is no known threat of apocalyptic asteroid collision for at least the next 100 years. But that doesn’t mean astronomers should stop looking. A bowling ball-sized meteor, for example, exploded over Vermont in March 2021 with the force of 440 pounds (200 kilograms) of TNT. Even more dramatically, a meteor explosion above Chelyabinsk, Russia, in 2013 produced a blast roughly equivalent to 400 to 500 kilotons of TNT, or 26 to 33 times the energy released by the Hiroshima bomb, and injured approximately 1,500 people.
Space agencies all over the world are already planning how to deflect a dangerous asteroid if one ever comes our way. The Double Asteroid Redirection Test (DART) spacecraft redirected the nonhazardous asteroid Dimorphos off course on September 26, changing the asteroid’s orbit by 32 minutes in the first test of Earth’s planetary defense system.
China has also indicated that it is in the early stages of planning an asteroid-redirect mission. The country hopes to avoid a potentially catastrophic collision with our planet by launching 23 Long March 5 rockets into the asteroid Bennu, which will swing within 4.6 million miles (7.4 million km) of Earth’s orbit between the years 2175 and 2199.