A huge asteroid, almost half a kilometer in diameter, swept past Earth on Tuesday night. This was the closest approach in 35 years by a cosmic object, as big as an aircraft.

Many telescopes turned skywards, but nothing was to be seen with the asteroid invisible. The 400 meter wide ice rock was a perfectly stealthy intruder, not reflecting a ray of light. Stargazers were keen for the passing as this was a unique chance to study an asteroid without sending an expedition into the open.

The body`s closest approach to the planet was pegged at a distance of 325,100km (202,000 miles) at 6:28 pm EST. This is just within the moon`s orbit or 85 percent of the average distance between the Earth`s and Moon`s centers. From the space defence standpoint, this can be regarded as an incursion.

Scientists first spotted the spherical, coal-coloured asteroid six years ago and, on studying its route, were confident it posed no danger. The asteroid has been named 2005 YU55.

There was a zero chance of collision with Earth, but if the asteroid were to hit ground, it would create a crater the size of Moscow or, plunging into water, could raise a 20-meter (70-feet) tsunami wave.

The last similar encounter happened in 1976, although astronomers did not know about the flyby at the time. Another oversized interloper from space is expected to zoom towards Earth no earlier than in 2028.
sections: Nature & Health