Henry Lau, editor of physics.org, has put together a special news round-up to help grasp what happened last week when the meteorite hit Russia.
One of the biggest physics story this year has literally exploded on the news. A meteorite hit the Urals region in Russia on Friday morning UK time. On the same day, a different asteroid made the closest pass to the Earth in the history of monitoring these space threats, inside the orbit of geosynchronous orbits of communication satellites.
The Russian meteorite was caught by many in-car cameras (why Russians have in car cameras) and also many people who came out to see what the bright streak in the sky was. The explosion caused shockwaves that could be felt several hundred of kilometres away. Video rounds ups here and here.
Estimates from data from infrasound recordings, which were originally set up to detect nuclear blasts, put the size of the meteorite at 17m, small enough to have travelled undetected through space. The infrasound at a frequency of .4Hz-20Hz could be heard halfway round the world. As it entered our atmosphere it had a mass of around 10,000 tonnes, travelling at 40,000 mph, and had the same energy as a 500 kilotons explosion (~30 Hiroshima bombs).
The meteorite is thought to be made up of mainly iron or nickel, but if it contained carbon dioxide or water, that may have accentuated the impact of the sonic boom.
Most of the damage in the region was caused by the sonic boom of the meteorite as it encountered our atmosphere. Part of the meteorite burnt up, burning brighter than the sun, caused by friction as the meteorite through the air. As the meteorite is travelling so fast, air builds up in front of the meteorite, causing a build-up of pressure which is eventually released as a sonic boom (how sonic booms work). The sonic boom and intense change in pressure smashed windows and sent glass flying which is the cause of most of the injuries to over 1200 people. The damage has not been a blanket case and is probably due to the orientation of buildings and the sonic boom and resonant frequencies of glass.
Some people are using this opportunity to advocate a newer system for watching the skies as currently our technology is unable to pick up threats this small, but this will be hard given the difficulty in observing such small objects. This article looks at some of the current measure we are taking to keep an eye out for threats.
The last thing to note is that meteor strikes are actually quite common and the Earth receives about 10 a year, but they are normally much, much smaller and just burn up in the atmosphere. The Guardian’s datablog has mapped every meteorite landing that we know of.
And then, on cue, as I write, there is news just in is that pieces of meteorites have now been found.
In other (slightly less exciting) news, the asteroid 2012 DA14 passed closer than we’ve ever recorded, and is predicted to be the closest any object has come to Earth. It was filmed passing over and made NASA’s APOD. For information, animations, videos and answers to questions about the asteroid from NASA, visit here.
For more general stuff about meteor, meteorites, asteroids check out physics.org.
Comet vs asteroid [video]
Guardian’s FAQ about the Russian meteorite