The asteroid 2005 YU55, discovered Dec 28, 2005 and a 400-metre piece of rock, will fly by the Earth at 5.15 a.m. Its closest distance from the earth will be around 3,25,000 km, which is lesser than the average earth-moon distance of 3,84,000 km, says Debiprosad Duari, director, Research and  Academic, M.P. Birla Planetarium, Kolkata.

He said scientists all over the world have been busy in calculating its possible path, as it zooms past the earth. The asteroid can be observed through an eight inch telescope.

"Although classified as a potentially hazardous object, 2005 YU55 poses no threat of an earth collision over at least the next 100 years. However, this will be the closest approach to date by an object this large that we know about in advance," Duari said in a statement.

The next time a known asteroid this large will come this close to earth will be in 2028 when (153814) 2001 WN5 passes at a distance of 2,48,000 km from the earth.

According to astronomers who are observing the approaching piece of rock, the 55 million tonne weight asteroid is jet black in appearance, spherical in shape, is 1,300 feet long and makes a full rotation in roughly 18 hours.

It goes round the sun once in 1.22 years.

"On its approach towards the earth, the gravitational influence of the asteroid will have no detectable effect on anything on earth, including our planet's tides or tectonic plates," he said.

Scientists are planning to make detailed observations of the approaching member of the solar system. During tracking, scientists will use the radio antennae at Goldstone and Arecibo to bounce radio waves off the space rock.

NASA scientists hope to obtain images of the asteroid as fine as about 7 feet (2 meters) per pixel. This should reveal a wealth of details about the asteroid's surface features, shape, dimensions and other physical properties, Duari said.