MONTREAL - 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 — 27,600 kilometres.

It is expected to pass over the Indian Ocean at around 2:30 p.m. EST.

asteroid da14

"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.

Asteroid 2012 DA14 is the same size as a space boulder that exploded over a wooded area in Siberia in 1908 in what became known as the Tunguska event. About 2,000 square kilometres of trees were flattened in an uninhabited area.

"It was not detected before impact," Brown added. "Although with the current telescopic surveys that are going on, there's a reasonable chance that an object like Tunguska could be detected before it impacted the Earth."

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."

Alan Hildebrand of the University of Calgary says studies are already being done to see how a threatening asteroid can be deflected.

"People have talked of many different concepts for moving or diverting asteroids," the planetary scientist said in an interview.

One option would involve exploding a device near an asteroid while another would use a spacecraft to pull it away.

"Some people would say you fly a spacecraft alongside and just the mass of the spacecraft will pull it — that's the gravity tractor idea," he said.

There's also the notion of using lasers or an ion beam to vaporize some of the surface of an asteroid.

Hildebrand will get a chance to take a closer look at asteroids when NEOSSat, a Canadian satellite, blasts off from India on Feb. 25. He's one of the project's principal investigators.

NEOSSat (Near Earth Object Surveillance Satellite) will circle the globe every 100 minutes and scan areas near the sun to pinpoint as yet undetected asteroids.

The $15-million suitcase-sized satellite, which will circle about 800 kilometres above the Earth, is the first dedicated space telescope to look for potentially hazardous asteroids.

"Our prime science mission is to search for the population of asteroids that orbit mostly inside Earth's orbit or entirely inside Earth's orbit," Hildebrand said.

"We're looking in the sky near the sun which is hard to do from the ground (and) we'll be filling in a part of orbital space which is poorly known so far."

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  • In this handout from NASA, the giant asteroid Vesta is seen in an image taken from the NASA Dawn spacecraft about 3,200 miles above the surface July 24, 2011 in Space. (Photo by NASA/JPL-Caltec via Getty Images)

  • This Feb. 14, 2000 photo provided by NASA shows the north pole of the asteroid Eros. The crater seen on the surface of Eros measures 4 miles across. (AP Photo/NASA)

  • This handout image provided by the European Space Agency, transmitted by the space craft Rosetta, shows the asteroid Lutetia at closest approach July 10, 2010 between Mars and Jupiter in outer space. (Photo by ESA 2010 MPS for OSIRIS Team via Getty Images)

  • This undated artist concept released by NASA and the Jet Propulsion Laboratory shows the Dawn spacecraft with Ceres and Vesta seen in the background. The spacecraft was captured into orbit around the massive asteroid Vesta after a 1.7 billion-mile journey and is preparing to begin a study of a surface that may date to the earliest era of the solar system, the space agency said Monday, July 18, 2011, in Pasadena, Calif. (AP Photo/William K. Hartmann/UCLA/NASA, JET PROPULSION LABORATORY)

  • This handout photo illustration provided by the European Space Agency, transmitted by the space craft Rosetta, shows the final sequence of images before the closest approach of the asteroid Lutetia July 10, 2010 between Mars and Jupiter in outer space. (Photo by ESA 2010 MPS for OSIRIS Team via Getty Images)

  • This handout image provided by the European Space Agency, transmitted by the space craft Rosetta, shows a close-up view of a possible landslide and boulders at the highest resolution on the asteroid Lutetia July 10, 2010 between Mars and Jupiter in outer space. (Photo by ESA 2010 MPS for OSIRIS Team via Getty Images)

  • This artist's concept provided by NASA illustrates the first known Earth Trojan asteroid, discovered by NEOWISE, the asteroid-hunting portion of NASA's WISE mission. The asteroid is shown in gray and its extreme orbit is shown in green. Earth's orbit around the sun is indicated by blue dots. The objects are not drawn to scale. The asteroid's orbit is well defined and for at least the next 100 years, it will not come closer to Earth than 15 million miles (24 million kilometers). (AP Photo/NASA - Paul Wiegert)

  • Computer modeling shows that the parent object of asteroid (298) Baptistina, which was approximately 170-kilometers in diameter with characteristics similar to carbonaceous chondrite meteorites, was disrupted 160 million years ago when it was hit by another asteroid estimated to be 60-kilometres in diameter.The extinction of the dinosaurs 65 million years ago can be traced to a collision between two monster rocks in the asteroid belt nearly 100 million years earlier, scientists reported on September 5, 2007. The two pictures on the right show remnants of the collision impacting the Earth and Moon. (DON DAVIS/AFP/Getty Images)

  • This image of the Asteroid Vesta, released by NASA/Jet Propulsion Laboratory on Monday, August 1, 2011, was captured by the Dawn spacecraft on July 24, 2011 at a distance of 3,200 miles (5,200 kilometers). (AP Photo/NASA, Jet Propulsion Laboratory)

  • This July 23, 2011 image of the Asteroid Vesta, released by NASA/JPL, was captured by the Dawn spacecraft at a distance of 3,200 miles (5,200 kilometers). (AP Photo/ NASA/JPL)

  • This undated artist rendition released by NASA/JPL shows the Dawn spacecraft orbiting the asteroid Vesta. (AP Photo/NASA/JPL)

  • This image released by NASA/JPL on Thursday July 28, 2011 shows an image of the dark side of Vesta asteroid captured by NASA'S Dawn spacecraft on July 23, 2011, and taken from a distance of about 3,200 miles (5,200 kilometers) away from the giant asteroid. (AP Photo/NASA/JPL)

  • This image of the Asteroid Vesta, released by the Jet Propulsion Laboratory in Pasadena, Calif., Monday, July 18, 2011, was captured by the Dawn spacecraft on July 17, 2011. The image was taken from a distance of about 9,500 miles (15,000 kilometers) away from the proto planet Vesta. (AP Photo/ NASA/JPL)

  • This image of the Asteroid Vesta, released by the Jet Propulsion Laboratory in Pasadena, Calif., Monday, July 18, 2011, was captured by the Dawn spacecraft on July 1, 2011. The image was taken from a distance of about 62,000 miles (100,000 kilometers) away from the protoplanet Vesta. Each pixel in the image corresponds to roughly 5.8 miles. (AP Photo/ NASA)