A team of researchers has detected a trio of near-Earth asteroids in the inner solar system, one of which is the largest found since 2014 that poses a potential risk to the planet. The asteroids remained undetected until now because they occupy a region of the sky hidden by the Sun’s glare.
Near-Earth Asteroids (NEAs) and Potentially Hazardous Asteroids (PHAs) are two types of near-Earth objects that space agencies like to keep track of. Despite the scary-sounding names, none of them pose any imminent threat to us. Currently, there are 1,454 NEAs that have a non-zero probability of impacting Earth in the next 100 years. You can find a complete list of NEOs at NASA’s Center for Near Earth Object Studies.
The three near-Earth asteroids were found using the Dark Energy Camera in Chile. The camera took deep-field images close to Earth’s horizon during twilight, to combat the Sun’s glare and atmospheric distortions. The team’s results are published in The Astronomical Journal.
“Our twilight survey is scouring the area within the orbits of Earth and Venus for asteroids,” said Scott Sheppard, an astronomer at the Earth and Planets Laboratory of the Carnegie Institution for Science and the paper’s lead author, in a NOIRLab release. “So far we have found two large near-Earth asteroids that are about 1 kilometer across, a size that we call planet killers.”
Two of the recently observed asteroids have orbits that safely skirt Earth, but one of the rocks—a 0.93-mile-wide (1.5-kilometer) asteroid dubbed 2022 AP7—has an orbit that may eventually put it on a collision course with Earth.
To be perfectly clear: The asteroid is not currently barreling toward Earth, but its path could bring it close enough one day that NASA will want to keep tabs on it.
If the worst were to happen, space agencies on Earth would have their first real-world (or real off-world) situation to employ an asteroid defense maneuver like the recent DART mission, which intentionally smashed into an asteroid named Dimorphos in September, slightly altering the asteroid’s orbital trajectory. The success of DART means NASA can now develop a more robust planetary defense strategy, should we ever need to redirect a threatening rock.
Somewhat counterintuitively, it is easier to detect asteroids beyond the Sun that it is to detect those between the star and Earth. Space-based observatories like Hubble and Webb always face away from the Sun, because the star’s intense light and heat could fry the observatories’ instruments.
That makes the work of the Dark Energy Camera all the more important—in the recent case, it found a potential threat to Earth that might otherwise have remained invisible to us.
Last month, researchers released a sweeping report on near-Earth asteroids using radar data from the now-destroyed Arecibo Observatory radio telescope. Their findings, published in The Planetary Science Journal, provided new insights about the motion of near-Earth asteroids from December 2017 to December 2019.