The north Queensland sky was briefly set alight on Saturday night as a meteor blazed through the atmosphere, exploded, and came to earth with a tremendous boom.
Footage captured on smartphones, dashcams and security cameras by businesses and residents from Cairns on the east coast to Normanton on the Gulf of Carpentaria circulated on social media on Sunday, showing a fireball growing rapidly in size as it approached the Earth, followed by a blast of greenish-blue light.
Colour footage captured by Cairns airport showed the sky lighting up green and then yellow as the meteor approached just after 9.22pm on Saturday.Residents in the small town of Croydon, about 500km west of Cairns, said on social media that they had also felt an explosion and heard a huge bang.
Dr Brad Tucker, an astrophysicist at Australian National University, told Guardian Australia the rock was likely between 0.5 and 1 metre in size, making it a smaller to average sized meteor, and was likely travelling up to 150,000km/h.
Most meteors are made of stony chondrite, but the greenish colour prior to impact in this case was most likely caused by overheating of iron and nickel fragments as the rock broke apart before it hit the ground.
The impact of the rock with Earth would not have left a crater, Tucker said, as the rock would have fragmented considerably by the time it reached the surface.
Despite its flaming appearance, caused by friction on its entry into the atmosphere, most of the rock would still be frozen by the time it landed.
“It essentially does a belly flop. The friction builds up and causes that glow and then it hits breaking point, which causes the huge flash and the sonic boom,” Tucker said.
Tucker said the sonic boom was “the part we worry about with most meteors”.
“It’s a mid-air detonation, so if it’s over a populated area, that can cause the damage,” Tucker said. “This one is on the small side, but we worry about the 10-metre, 20-metre sized meteors.”
In 2013, a 20-metre meteor exploded over the Russian city of Chelyabinsk. Scientists found the rock exploded with the energy of 500 kilotonnes of TNT. The explosion knocked people off their feet, shattered windows in 3,600 apartment buildings, and caused a factory roof to collapse. At its most intense, the Chelyabinsk meteor glowed 30 times brighter than the sun, leaving people up to 18 miles away from it with skin and retinal burns.
Meteors crash through the Earth’s atmosphere like this every month or so, Tucker said, but as most of the surface area of the Earth was uninhabited, most of them went unheeded by the general public.
“This one happened at a convenient time in a relatively populated area – 9pm on a Saturday night means lots of people are going to see it.”
Quelle: The Guardian