An asteroid about half the size of a football field will make a very close visit to Earth on Friday and will even be affected by the planet's gravitational pull. Asteroid 2012 DA14 will pass inside the ring of satellites that circle the planet, but scientists say Canadians shouldn't be worried about a collision.

Peter Brown, a scientist at Western University in London, Ont., says it's the largest asteroid on record to pass so close to the Earth at 27,600 kilometres. It is expected to pass over the Indian Ocean at around 2:30 p.m. EST.

``Things of this size get this close to the Earth or closer only about once every 40 years,'' Brown, who studies asteroids and meteors, said in an interview. ''So it's an unusual event.``

The asteroid will come so close that the Earth's gravity will change its orbit, but it won't be dragged down.

``We know with absolute certainty it will not impact the Earth on Friday,'' Brown said. ``And we can say that there's a very low chance (maybe one chance in 300,000) that it will impact (the Earth) in the next 100 years or so.''
    
Brown said the asteroid will be visible by binoculars in areas like Indonesia, eastern Europe, Asia and Australia, although it will be moving very fast. It will be visible from North America later in the evening but only with high-powered telescopes.

NASA will provide coverage on its website, beginning at about 2 p.m. EST.

Brown also pointed out that scientists have become better at understanding and documenting the orbits of potentially dangerous asteroids.

``There are about 1,000 asteroids that get fairly close to the Earth and cross the Earth's orbit that are one-kilometre in size,'' Brown said, adding the orbits of 90 per cent of them are known. ``So we can say with definitiveness that of all the ones that we have accurate orbital data for, none of them are going to hit in the next 100 years.''

(The Canadian Press)