An Astronomical First for Asteroids

Imagine an 80 tonne asteroid hurtling towards the Earth at 30,000 mph. It may sound like science fiction but in October 2008 this scenario was a potentially dangerous reality.
 

In 1908 an asteroid exploded above Tunguska, Siberia, with a force equivalent to 10-15 million tonnes of TNT. Today, experts at the Rutherford Appleton Laboratory assess the hazards posed by Near Earth Objects and can advise on what action to take to minimise the danger from any impact, air-blast or debris.

 
Fortunately UK astronomers detected the asteroid using the STFC’s William Herschel Telescope on La Palma hours before it entered our atmosphere. It was the first time astronomers could study an asteroid before it potentially hit the Earth and thus determine the level of threat to our planet.
 
By examining the asteroid’s reflected light, or spectrum, the astronomers gained crucial information on its size and composition. “It was important to try and figure out what type of asteroid it was before impact,” explained Professor Alan Fitzsimmons from Queen’s University Belfast. “The faint observed brightness implied a small size, which meant little advance warning.”
 
Fortunately, the four metre diameter asteroid 2008 TC3 did not hit the Earth directly and exploded in the atmosphere. “This event shows we can successfully predict the impact of asteroids – even with a short warning time – and obtain the astronomical observations necessary to estimate what will happen when the asteroid reaches us,” said Professor Fitzsimmons, whose research team is funded by STFC.
 
Small fragments of the asteroid survived the high-altitude explosion and were found in the Nubian Desert in Sudan. They showed that the astronomer’s data matched well and that the asteroid was a rare F-class type asteroid.

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