Asteroid impact danger diminishes

Fears of Armageddon receded further today after NASA scientists refined calculations of the path of a threatening asteroid. A giant space rock called Apophis is due to make two close approaches to Earth within the next 30 years.

Nasa impression of an asteroid strikeThe first, on Friday the 13th of April,  2029, is virtually certain to miss us though it will come closer than TV and other geostationary satellites, at a distance of only 18,300 miles.

But uncertainty over the effect of that close encounter meant that astronomers could not rule out the chance of an impact seven years later in 2036. There were some imaginative ideas to avoid this happening.

Now, however, the chance of a catastrophic collision on 13 April of that year have dropped from one-in-45,000 to an even more reassuring one-in-250,000.

Apophis is 300 yards wide and weighs 25 million tons. It was only discovered in December 2004.

If it struck, it would hit Earth with a force equivalent to 880 megatons – around 65,500 times the energy of the atomic bomb dropped on Hiroshima – which is why scientists have taken it so seriously.

The new calculations were carried out by specialists Steve Chesley and Paul Chodas at NASA’s Jet Propulsion Laboratory in Pasadena, California. They are due to present their latest findings at a meeting of the American Astronomical Society’s Division for Planetary Sciences in Puerto Rico tomorrow.

They based their figures on photographs of Apophis made by astronomers using telescopes on Mauna Kea, Hawaii, together with other data from Kitt Peak, Arizona, and Arecibo, Puerto Pico. Hundreds of images were analysed to refine the asteroid’s position and produce a path into the late part of the century.

Hawaii asteroid hunter Dr David Tholen helped analyse the images. He said: “Our new orbit solution shows that Apophis will miss Earth’s surface in 2036 by a scant 20,270 miles, give or take 125 miles. That’s slightly closer to Earth than most of our communications and weather satellites.”

As well as showing the reduced likelihood of an impact in 2036, the analysis revealed that Apophis will make another close encounter in 2068, although once more it is unlikely to present a danger.

• Discover space for yourself and do fun science with a telescope. Here is Skymania’s advice on how to choose a telescope. We also have a guide to the different types of telescope available.

Paul Sutherland

Paul Sutherland

I have been a professional journalist for nearly 40 years. I write regularly for science magazines including BBC Sky at Night magazine, BBC Focus, Astronomy Now and Popular Astronomy. I have also authored three books on astronomy and contributed to others.
Paul Sutherland

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Paul Sutherland

I have been a professional journalist for nearly 40 years. I write regularly for science magazines including BBC Sky at Night magazine, BBC Focus, Astronomy Now and Popular Astronomy. I have also authored three books on astronomy and contributed to others.

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