Astronomers around the world will be keeping a close watch as the menacing asteroid Apophis begins a sweep past Earth later today.

Sky watchers will also be able to go on the internet to view live images of the asteroid, which research shows could collide with the planet in 2036.

But over the next few days, Apophis will come within only 15 million kilometres of Earth. While that's way beyond the orbit of the moon and far enough away not to cause any concern, scientists said it will come even closer.

The asteroid is just over 300 meters in diameter and is made up of dense rock rubble held together by a gravitational pull.

Since it stays close to the sun, it wouldn’t have the same impact on the Earth’s surface as an asteroid that came from beyond the sun’s orbit.

"If it hits a city, it’s moving day, quite abruptly, for a lot of people," said Robert Dick, University of Ottawa astronomy instructor and member of the Royal Astronomical Society of Canada.

'If it hits a city, it’s moving day, quite abruptly, for a lot of people' —Robert Dick, astronomy instructor at the University of Ottawa

The asteroid has a slightly wonky orbit that brings it close to Earth roughly every six years. Wednesday’s fly-by will give astronomers a better idea of the asteroid’s make-up and will shed more light on its exact orbit.

"Earth is nicely behaved, this asteroid is a little loopy," said Dick. "It’s orbit is a little flat. Four times flatter than the Earth,"

Andrew Fazekas, a spokesman for the society, said the asteroid will pass about 30,000 kilometres above the Earth on the ominous date of April 13, 2029. It will be bright enough to see easily with the naked eye.

Fazekas said research done on near-Earth asteroids has shown there's a small chance there could be an impact with Apophis when it comes around again in 2036.

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Asteroid Apophis was discovered on June 19, 2004. (UH/IA)

But further calculations need to be done because the asteroid's orbit could be changed slightly by the gravitational pull from Earth after this year's visit.

Experts at NASA’s Near Earth Object (NEO) office calculated that the odds of the asteroid having an "Earth encounter" is approximately four in a million.

The asteroid once rated a four out of 10 on the Torino scale and was given a one-in-42 chance of striking Earth in 2036.

The Torino scale starts at zero, given to events of "no likely consequences." The scale ends at 10, with what the NEO office describes as a certain collision "capable of causing global climatic catastrophe that may threaten the future of civilization as we know it."

Fazekas says people will be able to go online at Slooh.com and view the asteroid live during its fly past.

The images will be provided by a robotic telescope located in the Canary Islands off the coast of Africa, beginning at 7 p.m. ET.

Near-Earth asteroids are not entirely uncommon. Astronomers have recorded approximately 9,000 of them to date, according to the astronomy news website Space.com.

Near misses

In May 2012, an asteroid about the size of an 18-wheeler truck called 2012 JU skimmed by within 191,500 kilometres of Earth.

In November 2011, the cruise-ship-sized 2005 YU55 came within 325,000 kilometres of Earth before continuing its journey through space.

The Arizona meteor crater is a kilometre-wide hole thought to have been made by a piece of cosmic iron ore 100 metres in diameter, while Sudbury's nickel deposits come from one of the largest space objects to hit Earth.

A crater that lies under Mexico's Yucatan Peninsula is believed to be the result of a meteor that is thought to have caused the extinction of dinosaurs 65 million years ago.

With files from The Canadian Press