A fireball exploded above the Bering Sea at about noon local time on December 18, 2018 from an asteroid with 10 times the energy of Hiroshima’s atomic bomb at a speed of 32 km/s (20 miles per second). The event went unobserved until military satellites spotted light the explosion released. The fireball was also spotted by Peter Brown at Canada’s University of Western Ontario, who announced his finding on Twitter. Brown looked at data taken from around 16 different infrared stations that were originally set up to listen for covert nuclear tests.
The BBC reports that it’s the biggest blast since the meteor that exploded over Chelyabinsk in Russia in 2015—and the second-biggest in 30 years. It was 10 meters across, and the energy released as it exploded in Earth’s atmosphere was equivalent to 173 kilotons of TNT. That’s about 10 times bigger than the atomic bomb used on Hiroshima in 1945.
“That was 40% the energy release of Chelyabinsk, but it was over the Bering Sea so it didn’t have the same type of effect or show up in the news,” said Kelly Fast, near-Earth objects observations program manager at Nasa. “That’s another thing we have in our defence, there’s plenty of water on the planet.”
Lindley Johnson, NASA’s first-ever Planetary Defense Officer,, told the BBC an explosion of this size takes place about two or three times every 100 years.
Image below: With thanks to barcroftmedia.com, BBC The Day the Dinosaurs Died