What happened at Chelyabinsk in 2013?
On 15 February 2013 a stony asteroid about 18–20 metres across exploded high above Chelyabinsk in Russia. The shock wave shattered windows across the region and injured around 1,500 people, mostly from flying glass.
On the morning of 15 February 2013, people across the Chelyabinsk region of Russia's southern Urals saw a fireball brighter than the Sun streak across a clear sky. It was a small asteroid, roughly 18 to 20 metres across and weighing something like 10,000 tonnes, travelling at about 19 km/s. Nobody had seen it coming, partly because it approached from the direction of the Sun, where telescopes cannot look.
The object broke apart violently at heights of around 30 km, releasing energy estimated at around 400 to 500 kilotonnes of TNT, roughly thirty times that of the Hiroshima bomb. Because the explosion happened so high, most of that energy reached the ground as a shock wave rather than a direct blast. It arrived a minute or more after the flash. Many people had gone to their windows to look at the strange light and trail, and were hit when the glass blew in. Around 1,500 people needed medical help, and thousands of buildings were damaged.
Thousands of meteorite fragments were later recovered from snowfields. The rock is an LL5 ordinary chondrite, a common kind of stony meteorite. The largest piece punched a hole in the ice of Lake Chebarkul and was hauled out months later; it weighed more than half a tonne.
Chelyabinsk was the largest known object to enter Earth's atmosphere since the Tunguska event of 1908, and it was recorded by dashcams, security cameras and satellites, giving scientists an extraordinary data set. By coincidence, a different asteroid passed close to Earth later the same day, but the two were unrelated. The event gave fresh urgency to surveys searching for small near-Earth asteroids.