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 asteroids.
Apophis 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.
We must accept that someday, we will be faced with the problem of dealing with an asteroid that will hit. Perhaps we won’t notice a small one until it’s too late and, if it hits a populated area, it could be destructive.
Wednesday’s pass of Apophis is only close by astronomical standards – 14.5 million kilometres above Earth’s surface. So we shouldn’t be concerned. Astronomers will get a nice view of the flyby. But on April 13 of 2029, Apophis comes in for a mighty close shave, less that one-tenth the distance of the moon and closer even than communication satellites that orbit Earth. That’s a bit nerve-jangling.
For more on the odds of our demise, see <a href=”http://www.amazon.com/gp/product/0143116045/”>Death from the Skies!: The Science Behind the End of the World, Philip Plait Ph.D.</a>. It makes you feel scared and relieved AT THE SAME TIME!