Asteroid Searches with Dark Energy Cameras and Future Space-based Astronomy Observatories: The Challenge of Observing the Inner Solar System

While NASA recently proved it can successfully alter the motion of an asteroid in space with September’s Double Asteroid Redirection Test, or DART mission, astronomers first must find space rocks that pose a threat to our planet. Instruments like the Dark Energy Camera, as well as future space-based observatories like the Near Earth Object Surveyor, can pinpoint previously unknown asteroids.

To avoid the sun’s glare, astronomers leaped at the chance to conduct their observations during the brief window of twilight. An international team spied the space rocks while using the Dark Energy Camera located on the Víctor M. Blanco 4-meter Telescope located at the Cerro Tololo Inter-American Observatory in Chile.

The main asteroid belt is located inside the inner solar system, which poses a challenge if they want to find space rocks. In order to avoid the harsh light of the sun, they only have two 10-minute windows each night to sweep the area with ground-based telescopes.

Since the asteroid takes five years to complete a round trip around the sun, it will occur whenever Earth is on the opposite side of the sun. When the asteroid is in alignment with Earth, its movement will be more consistent. Even though scientists don’t know the asteroid’s position with enough accuracy, it will stay away from Earth.

The closest known asteroid to the sun is 2021 PH 27. The surface of the space rock is hot enough to meld lead when it is close to our star.

If things sound complicated for ground-based telescopes, observations of the inner solar system are impossible for space-based telescopes like Hubble and James Webb because the sun’s heat and intense light could fry their instruments, which is why both space observatories are pointed away from the star.

“Large areas of sky are required because the inner asteroids are rare, and deep images are needed because asteroids are faint and you are fighting the bright twilight sky near the Sun as well as the distorting effect of Earth’s atmosphere,” Sheppard said. “DECam 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.”

Near-Earth objects are asteroids and comets that are close to Earth. Detecting the threat of near-Earth objects that could cause grave harm is a primary focus of NASA and other space organizations around the world.

Asteroids often have highly elliptical orbits, meaning they are sometimes closer to the Sun and sometimes much further away. To be able to forecast the path an asteroid will take you need at least 3 observations, each lasting at least 24 hours. Astronomers will often call up colleagues working with other telescopes to help get these crucial observations before an asteroid becomes too faint to see.

Sheppard isn’t worried about the Earth being destroyed anytime soon, but he does think we ought to be ready in case an asteroid could one day pose a danger. “I don’t think it’s an immediate threat, but you want to be prepared,” he said. “Right now, there’s nothing known that’s even a slight danger to the Earth. We have found most of the killers and now we are looking for the city killers.

When there is no Moon, it is like going out at night. When the Moon isn’t in use, it obscures the fainter stars and you can see many more. When attempting to spot faint asteroids in the glare of the Sun, something happens which is why big asteroids have remained hidden.

There are also space-based missions looking for near-Earth asteroids like the NEOWISE project and the upcoming NEO Surveyor. Unlike ground-based telescopes, these have the advantage of not having to deal with interference from Earth’s atmosphere and being able to detect fainter objects.

The upcoming Vera C Rubin Observatory will give us a huge boost in our ability to find asteroids by performing a survey that covers the whole southern sky every few nights with a much more powerful telescope than what is currently available.