Astronomers in the U.S. recently spotted three asteroids close to Earth. They were all traveling hidden by the Sun's brightness. Two of these are big enough to potentially wipe out human civilization and much of Earth's life. These asteroids are between the orbits of Earth and Venus. So, even though they're closer than we'd prefer, the intense brightness of the Sun makes them really hard to see. Basically, the Sun's light makes it tough for telescopes to pick them up.
To get a better look at these massive space rocks, astronomers did a twilight scan and used a Dark Energy Camera. This camera is part of the Victor M. Blanco 4-meter Telescope at the Cerro Tololo Inter-American Observatory in Chile. Their discoveries were then shared in an article in The Astronomical Journal.
One of these giant asteroids, named 2022 AP7, is about 1.5 km across. Its orbit might, in the future, intersect with Earth's. But predicting when is tricky because of the time these asteroids take to go around the sun. Bottom line, if there's a collision, it's not happening anytime soon.
Scott S. Sheppard, the main writer of the study and an astronomer at the Earth & Planets Lab of the Carnegie Institution for Science in Washington DC, commented, "Our twilight survey is scouring the area within the orbits of Earth and Venus for asteroids. So far we have found two large near-Earth asteroids that are about 1 kilometer across, a size that we call planet killers."
People believe that a massive asteroid over a kilometer in size would drastically change life on Earth. Moreover, the resulting debris and pollutants would cloud the atmosphere for several years, blocking sunlight from reaching the Earth's surface. "It would be a mass extinction event like hasn't been seen on Earth in millions of years."
How Threatening Are These Planet-Killer Asteroids?
Of the two, 2021 PH7 and 2021 LJ4, the first one really grabs the attention of scientists. 2021 PH7 is currently the asteroid closest to the Sun that we're aware of. Still, both their paths seem to pose less risk concerning Earth. Yet, when astronomers say 'near-earth,' they're talking about comets and asteroids that can get within 30 million miles of Earth during their journey. Identifying these potential hazards is a priority for NASA and other global space agencies. Right now, there's no known asteroid heading straight for Earth. But, there are over 27,000 asteroids in the "near-Earth" classification.
The newly identified big asteroid, 2022 AP7, is expected to approach Jupiter and Mars within the next 145 years. Adding to that, according to NASA's Paul Chodas, 2022 AP7 is "one of the most distant of the asteroids that we categorize as potentially hazardous." Also, of the 27,000+ near-Earth objects, just 857 are about half a mile wide – nowhere big enough to be catastrophic for the planet.
Notably, NASA's DART mission recently showcased that we can use spacecraft to nudge an asteroid and tweak its trajectory. To do this effectively, Chodas emphasizes that "the most important thing […] is to find them and to find them with lots of warning time." Current twilight scans using tools like the Dark Energy Camera are hoped to enhance our efforts in finding and alerting about such space rocks.