Update on the fireball that exploded over Russia

The largest ~ 1 kilogram (2.2 lbs) Chelyabinsk / Chebarkul meteorite found to date alongside many smaller fragments. Credit: Screenshot from video, courtesy press-service Ural Federal University

The sun rose twice over the Ural Mountains in Russia Friday February 15. No one expected the second sun, a meteoroid that slammed into the atmosphere so fast it set the air aglow with a fire even brighter than the real sun. It lasted more than 30 seconds before exploding and sending a shock wave rippling across the city of Chelyabinsk and surrounding countryside.

Thousands of residents of small towns in the area of the fall at and around Lake Chebarkul have been busy hunting for meteorite fragments by looking for holes in the snow cover and then carefully clearing away the white stuff until a little black rock remains. It must sound and look like an Easter egg hunt out there. Some of the locals are cashing in on meteorite fever by offering rides to the big hole in the ice on Chebarkul Lake thought to have been punctured by a meteorite fragment.

Another view of the biggest meteorite fragment. It’s shows regmaglypts or dimples created when high temperatures during entry heat and melt away minerals on the surface. Click to see more images of  meteorites found from the fall. Credit: Screenshot from video, courtesy press-service Ural Federal University

Many of the stones – some real, some obviously fake – are popping up on various auction sites in Russia and elsewhere. A quick check on eBay under “Chelyabinsk meteorite” turned up 29 listings today. How many of those are real? Hard to say.

One meteorite hunter interviewed by a BBC team put it this way: “It’s like hunting or fishing. When you see an animal, your heart starts to beat fast, and when you’re fishing – it’s like pulling the fishing rod and thinking there’s something extraordinary. This is the same – you see a tiny hole, try it, and here it is.”

After more than a week of study, we know a little more about the asteroid that created this shower of stones in large part from information recorded by a network of infrasound sensors operated by the Comprehensive Test Ban Treaty Organization (CTBTO). Their purpose is to monitor nuclear explosions.

https://www.youtube.com/watch?v=H-8ij80vs1E
Recording of infrasound from the Russian fireball that’s been sped up 135 times so we can hear it. The original file was 25 minutes long!

Infrasound, a very low frequency sound wave that can travel long distances, can only be heard by a few animals including elephants. When a large meteor enters the atmosphere it sends ripples of infrasound across the atmosphere around the planet revealing information about its speed, direction of travel and how much energy it contains.

“The Russian meteor’s infrasound signal was was the strongest ever detected by the CTBTO network. The furthest station to record the sub-audible sound was 9,300 miles away in Antarctica,” according to a NASA press release.

Russian fireball on Feb. 15, 2013 recorded by a dashcam

Here’s what we know based on an analysis by Western Ontario Professor of Physics Peter Brown:

* Size: 56 feet (17 meters) in diameter
* Weight: 11,000 tons (10,000 metric tons)
* Speed: 40,000 mph (64,000 km/hour) and broke apart 12-15 miles above Earth’s surface
* Exploded with the power of 470 kilotons of TNT which is equal to more than 23 1940s-era atomic bombs

We looked at the asteroid’s orbit the other day and discovered it belonged to the Apollo family of Earth-crossing asteroids. When farthest from Earth it used to mingle with its many friends in the asteroid belt. Like the majority of asteroids between Mars and Jupiter it has a rocky composition.

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