map of Africa and Madagascar, Australia region with blue line showing Madagascar asteroid impact and red line showing Africa impact
Impact time and location predictions for asteroid 2018 LA. The long blue bar shows the predictions prior to ATLAS data being obtained. The much shorter red bar in the image shows the prediction including ATLAS data, while the yellow star marks the actual location. ATLAS clearly made it possible to associate the impact with the observed asteroid. (Credit: Aren Heinze, IfA/ATLAS; Brooks Bays, SOEST; Bill Gray, Project Pluto)

An international team of scientists just found the first fragments of the small asteroid 2018 LA, which exploded harmlessly high above Africa on June 2. The University of Hawaiʻi’s Asteroid Terrestrial-Impact Last Alert System (ATLAS) telescope took the final images of 2018 LA before it entered Earth’s atmosphere and exploded.

Although 2018 LA was discovered by a different telescope in Arizona, ATLAS played a crucial role in determining the asteroid’s final destination. Prior to the ATLAS measurement, impact predictions showed 2018 LA hitting the Earth anywhere from Madagascar to the South Pacific—a range spanning almost half Earth’s southern hemisphere.

By measuring the asteroid more than two hours after it was last seen from Arizona, and less than 5 hours before it exploded, ATLAS greatly improved the accuracy with which the pre-impact orbit could be calculated, helping to prove the bright meteor subsequently seen over Botswana was indeed the fiery demise of 2018 LA.

What makes this especially satisfying to Hawaiʻi’s ATLAS team is that the robotic telescope wasn’t specifically aimed at 2018 LA: it found the asteroid while automatically scanning the sky—exactly what the telescope is designed to do.

ATLAS consists of two telescopes, 100 miles apart, with one on Mauna Loa on Hawaiʻi Island, and one on Haleakalā, Maui. They automatically scan the whole sky several times every night looking for moving objects. The goal of the ATLAS survey is to look in all directions and see asteroids before they can hit the Earth.

“This is a great test of the system,” said Larry Denneau, ATLAS Principal Investigator from the Institute for Astronomy. “We’ve confirmed that ATLAS can find impactors. If 2018 LA had been big enough to cause a dangerous explosion, like the asteroid that hit Russia in 2013, we’d have had enough warning that people could evacuate the impact zone.”

For the first time in history, astronomers can provide sufficient warning to move people away from the impact site.

For more, read the Institute for Astronomy news release.

—By Roy Gal