An artist’s impression of the asteroid. | SkyNews
An artist’s impression of the asteroid. (NoirLab)

Astronomers discover largest asteroid threat in nearly a decade

2022 AP7 is 1.5 kilometres wide and its orbit could someday be put in Earth’s path.

Astronomers have discovered three near-Earth asteroids (NEAs) blending in with the Sun’s glare. One of them is the largest potential object threat to the planet to be discovered in eight years, according to NoirLab.

The asteroids were discovered by a team at the Cerro Tololo Inter-American Observatory in Chile using a Dark Energy Camera.

“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,” said Scott S. Sheppard, an astronomer at the Earth and Planets Laboratory of the Carnegie Institution for Science. 

He is also the lead author of the paper called A Deep and Wide Twilight Survey for Asteroids Interior to Earth and Venus.

The asteroids are part of a larger group of asteroids hiding inside the orbits of Earth and Venus. The largest one is 1.5 kilometres wide and is called 2022 AP7. Its orbit could someday be put in Earth’s path, which makes the lessons learned from NASA’s successful Double Asteroid Redirection Test (DART) mission important. The other asteroids, 2021 LJ4 and 2021 PH27, are not a threat to the planet. 

Astronomers and astrophysicists are interested in 2021 PH27, because it is the closest known asteroid to the Sun. This means it has our Solar System’s largest general-relativity effects. Its surface can also get hot enough to melt lead.

There are likely a few NEAs with similar sizes left within this region of space, which is difficult to do from the ground because of the Sun’s glare. Any observations are made by looking close to the horizon during two brief, 10-minute windows. The team discovered the trio at twilight.

Watching the area with a space-based telescope is impossible. The Sun’s heat and light would fry the electronics onboard, which is one reason space telescopes are pointed away from the sun. 

“[The Dark Energy Camera] can cover large areas of sky to depths not achievable on smaller telescopes, allowing us to go deeper, cover more sky, and probe the inner Solar System in ways never done before,” said Sheppard.

According to NoirLab, the Dark Energy Camera was originally built to carry out the Dark Energy Survey used in Sheppard’s paper, which was conducted by the U.S. Department of Energy and the U.S. National Science Foundation between 2013 and 2019.