A meteor caused a massive explosion over Earth last year, but nobody noticed until now. It is the second-largest recorded impact in the past century, after the meteor that exploded over the Russian region of Chelyabinsk in 2013.
The giant fireball hit at 2350 GMT on 18 December over the Bering Sea, a part of the Pacific Ocean between Russia and Alaska. Peter Brown at the University of Western Ontario, Canada, spotted the meteor in measurements picked up by at least 16 monitoring stations globally. The meteor was 10 metres in diameter, had a mass of 1400 tonnes and impacted with an energy of 173 kilotons of TNT, he wrote on Twitter.
The impact energy was about 10 times that of the atomic bomb dropped on Hiroshima in 1945. The meteor exploded at altitude above Earth’s surface, says Alan Fitzsimmons of Queen’s University Belfast, UK. “It would have been quite spectacular,” he says.
The explosion was detected by infrasound stations around the world, which pick up low-frequency acoustic waves inaudible to humans. These stations were initially set up during the cold war to detect nuclear explosions.
It is the third-largest impact in modern times, after Chelyabinsk and a massive explosion that occurred in Siberia, Russia, in 1908. Known as the Tunguska event, the air burst flattened an estimated 80 million trees over an area of more than 2000 square kilometres. “When you see these infrasound waves, you know immediately that there has been an impact or a large release of energy,” says Fitzsimmons.
Triangulating the location and source of an explosion requires combining pressure wave data from multiple monitoring stations, which may explain the delay in the data being made public. The Bering Sea explosion was also picked up by US government monitors that detect fireballs: their sensors pick up electromagnetic radiation in the form of infrared and visible light.
The first British-led expedition to gather meteorites in the Antarctic has returned with a haul of 36 space rocks.
Manchester University’s Dr Katherine Joy was dropped in the deep field with British Antarctic Survey guide Julie Baum for four weeks.
The pair spent their days near the Shackleton mountains running across the ice sheet in skidoos looking for out-of-place objects.
The meteorites ranged from tiny flecks to some that were as big as a melon.
Some two-thirds of the meteorites in the world’s collections have been picked up in the Antarctic. It’s the contrast of black on white that makes the continent such a productive hunting ground.
“As soon as you spot a black rock you know. You dart towards it and your heart picks up a beat,” Dr Joy told BBC News.
“They look black because they’re burnt up as they come down through Earth’s atmosphere. They have a very characteristic exterior colour, and they have a kind of cracked surface where that exterior has expanded and contracted during the violent atmospheric entry.”
It was an astronomically exciting weekend for stargazers – people from around the North Island witnessed a possible meteor or space junk sighting about 9pm on Saturday.
The rare event tore across the sky above the Sri Lanka versus New Zealand cricket match at Bay Oval, Mount Maunganui. Footage from the match captured several pieces moving in a bright cluster, breaking up before being swallowed into the dark of the night sky.
Aficionados were quick to dispel theories it was a meteor, claiming it was more likely to be space junk. But what was it?
Experts have named a Russian military satellite – Kosmos 2430, a satellite launched in 2007 as part of Russia’s Oko space programme – as the most likely object that lit up the sky.
While some satellites stay above the same spot on Earth, Kosmos 2430 orbited an area above the northern hemisphere giving it time to look over the United States. Its entire orbit would take about 12 hours.
SO WHERE DID IT LAND?
As ships, stations, and other satellites come crashing down to Earth, many end up making planet-fall at the same spot in the Pacific Ocean just south of New Zealand, according to Atlas Obscura.
For years these downed science vessels have simply sunk down to the bottom of the sea in a place now known as the Spacecraft Cemetery.