Apophis – a 'potentially hazardous' asteroid – flies by Earth on Wednesday | Stuart Clark

Asteroid Apophis arrives this week for a close pass of Earth. This isn't the end of the world but a new beginning for research into potentially hazardous asteroidsApophis hit the headlines in December 2004. Six months after its discovery, astronomers had accrued enough images to calculate a reasonable orbit for the 300-metre chunk of space rock. What they saw was shocking. There was a roughly 1 in 300 chance of the asteroid hitting Earth during April 2029. Nasa issued a press release spurring astronomers around the world to take more observations in order to refine the orbit. Far from dropping, however, the chances of an impact on (you've guessed it) Friday 13 April 2029 actually rose. By Christmas Day 2004, the chance of the 2029 impact was 1 in 45 and things were looking serious. Then, on 27 December astronomers had a stroke of luck.Looking back through previous images, they found one from March on which the asteroid had been captured but had gone unnoticed. This significantly improved the orbital calculation and the chances of the 2029 impact dropped to essentially zero. However, the small chance of an impact in 2036 opened up and remains open today.While there is no cause for alarm, similarly there is no room for complacency either. Apophis remains on the list of Potentially Hazardous Asteroids compiled by the International Astronomical Union's Minor Planet Center.Although most asteroids are found in the belt of space between Mars and Jupiter, not all of them reside there...
Source: Guardian Unlimited Science - Category: Science Authors: Tags: Blogposts Astronomy guardian.co.uk Space Science Source Type: news