Meteor explosion largest infrasound recorded

By Paul Harper

The meteorite contrail is seen over a vilage of Bolshoe Sidelnikovo 50 km of Chelyabinsk. Photo / AP
The meteorite contrail is seen over a vilage of Bolshoe Sidelnikovo 50 km of Chelyabinsk. Photo / AP

Sub-audible infrasonic waves from the meteor which exploded over a remote region of Russia last week were recorded 15,000km away in Antarctica.

The low frequency sound from the meteor was the largest ever recorded by the Comprehensive Nuclear-Test-Ban Treaty Organisation's International Monitoring System, the agency says.

The blast was detected by 17 infrasound stations in the CTBTO's network, which tracks atomic blasts across the planet. Infrasound is low frequency sound with a range of less than 10 Hz and cannot be heard by people.

Until last week's meteor, the bolide explosion above Sulawesi, Indonesia, in October 2009 was the largest infrasound event registered by the CTBTO's network.

"We saw straight away that the event would be huge, in the same order as the Sulawesi event from 2009. The observations are some of the largest that CTBTO's infrasound stations have detected," CTBTO acoustic scientist, Pierrick Mialle says.

Like meteor blasts, atomic explosions produce their own distinctive, low frequency sound waves that can travel across continents.

The CTBTO has filtered and accelerated the audio so it can be heard by human ears here.

The European Space Agency say the first firm details of the February 15 meteorite impact over the Ural Mountains - the largest in more than a century - are becoming clearer.

The ESA says the information could be crucial in the development of the agency's asteroid-hunting efforts.

The space rock entered the atmosphere at 3.20am GMT (4.20pm NZT), exploding about 15-20km above Chelyabinsk.

Video footage shows the meteor took a northeast to southwest path at a shallow angle of 20 degrees above the horizontal. It is estimated to have entered the atmosphere at about 18km/s - more than 64,000km/h.

The first firm details of the 15 February asteroid impact in Russia, the largest in more than a century, are becoming clear. ESA is carefully assessing the information as crucial input for developing the Agency's asteroid-hunting effort.

At 3.20am, a natural object entered the atmosphere and disintegrated in the skies over Chelyabinsk, Russia.

Extensive video records indicate a northeast to southwest path at a shallow angle of 20° above the horizontal. The entry speed is estimated at around 18 km/s - more than 64 000 km/h.

According to calculations by Peter Brown at the University of Western Ontario, Canada, the object was about 17m across with a mass of 7000-10,000 tonnes when it hit atmosphere, and exploded with a force of nearly 500 kilotons of TNT - some 30 times the energy released.

Almost 1,500 people were injured by the meteor, which damaged about 3,000 buildings in the region.

Russian scientists have uncovered at least 53 fragments of the meteorite from the ice-covered Chebarkul Lake.

-nzherald.co.nz

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