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Asteroid Tracked From Space to Earth Entry for the First Time

03/28/2009 07:31PM

Asteroid Tracked From Space to Earth Entry for the First Time
The first predicted impact of an asteroid with the Earth has been studied by astronomers from Queen's University Belfast and a team of fellow international researchers. The impact occurred last October 2008.

The astronomers from Queen’s Astrophysics Research Centre (ARC) observed the asteroid as it was hurtling towards our planet and captured the only spectrum of it before it exploded in our atmosphere.

The observation is the very first time that an asteroid of any size has been studied before entering our atmosphere. This meant the scientists could predict whether it would explode and break up in the atmosphere or reach the ground, which determines whether an asteroid poses a threat.

"This was the first ever predicted impact of an asteroid with the Earth and the very first time an asteroid of any size has been studied before impact," said Professor Alan Fitzsimmons, from Queen's.

“The faint observed brightness implied a small size, which in turn meant there was little advance warning. It was important to try and figure out what type of asteroid it was before impact in order to give us a better idea of its size and where it came from. This event shows that astronomers 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.”

The asteroid in question, 2008 TC3, weighed 80 tonnes and had a diameter of 4 metres. It landed in the Nubian Desert in Sudan where it scattered after exploding at an altitude of 37km.

It was tracked thanks to a lucky coincidence which saw astronomers from two institutions in Northern Ireland at the William Herschel Telescope on La Palma at the same time; Sam Duddy and Dr Henry Hsieh from Queen’s and Dr Gavin Ramsay from The Armagh Observatory.

Sam said: “Dr Gavin Ramsay from the Armagh Observatory was scheduled to use the telescope that night. When we realised this was an unusual event, Dr Ramsay agreed to help us observe it. It was an exciting couple of hours planning the details of the observations. Performing the observations of an object that was certain to impact the atmosphere was a great but challenging experience.”

Dr Ramsay added: “These observations were technically quite difficult. The William Herschel Telescope, funded by the Science and Technology Facilities Council, really rose to the challenge, demonstrating what a versatile telescope it is. There was a great sense of excitement in the control room.”

Some small fragments survived the high-altitude explosion that vaporised most of the delicate asteroid . Dr Peter Jenniskens of the SETI Institute in California, teamed up with Dr Muawia Shaddad and 45 students of the University of Khartoum to search the Nubian Desert. 15 meteorites were recovered over an area 29km long along the calculated approach path of the asteroid.

According to Dr Jenniskens: “The recovered meteorites were unlike anything in our meteorite collections up to that point. The asteroid has been confirmed as a rare type called F-class, corresponding to dark ureilite achondrite meteorites with a texture and composition unlike any other ureilite meteorites found on earth before.”

The spectrum gathered by the astronomers allowed them to establish the first direct link between an asteroid and the individual meteorites produced as it breaks up in our atmosphere.

Comparing the asteroid and meteorite data tells us that 2008 TC3 may have only spent a few million years existing in the inner Solar system before it hit our planet.

Professor Richard Crowther of the Science and Technology Facilities Council (STFC) and Chair of the UN Working Group that deals with Near Earth Object (NEO) threats said: "The search for and study of asteroids is extremely important as not all impacts are as harmless as this small one in October. Larger impacts of the size associated with the Tunguska event of 1908 occur every few hundred years and even larger impacts with asteroids and comets the size of mountains occur every few tens of millions of years. Any extra knowledge we can gain about asteroids will help us mitigate the potential effects of such impacts in the future.”

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