Sheppard discusses future of daylight-side asteroid surveys in Science

New Asteroid, Sun and Mercury.jpg
An artist’s conception of the newly discovered asteroid 2021 PH27, which has the shortest known orbital period for an asteroid and second shortest for any object in our Solar System after Mercury. Illustration by Katherine Cain courtesy of the Carnegie Institution for Science.
Friday, July 22, 2022 

Carnegie astronomer Scott Sheppard recently wrote a perspective piece in Science detailing the search for asteroids lurking on the sunny side of Earth. 

Most asteroid searches occur at night with telescopes directed out to the far reaches of our Solar System in order to avoid the glare of the Sun. Sheppard points out that this leaves a big gap in our understanding of Near Earth Objects (NEOs) that could be orbiting between the Sun and Earth. 

Mathematical models suggest that more than 90% of "planet-killer" NEOs—asteroids larger than 1km— have been found. Sheppard thinks that the remaining large asteroids are likely orbiting closer to the Sun, where our normal asteroid surveys don't look. 

"The last few unknown 1-km NEOs likely have orbits close to the Sun or high inclinations, which keep them away from the fields of the main NEO surveys," writes Sheppard. 

We have the technology! Recently, scientists like Sheppard have begun searching at twilight to avoid the glare of the Sun. He uses the Dark Energy Camera (DECam) on the CTIO Blanco 4-meter telescope in Chile for his Twilight Survey. These new surveys are beginning to find asteroids, both large and small, in this interior orbit.

"New telescopic surveys are braving the Sun’s glare and searching for asteroids toward the Sun during twilight. These surveys have found many previously undiscovered asteroids interior to Earth, including the first asteroid with an orbit interior to Venus, ’Ayló’chaxnim (2020 AV2), and an asteroid with the shortest-known orbital period around the Sun, 2021 PH27," writes Sheppard. 

2021 PH27 was discovered in 2021 by Sheppard himself.

As these Sun-ward surveys begin to find more asteroids, astronomers will get a better picture of what the NEO asteroid population truly looks like.