New Delhi: Thousands of sky enthusiasts and students on May 7 thronged the Nehru Planetarium as planet Mercury passed across the Sun while planetorium authorities made arrangements to view the rare celestial event through telescopes.

"The mercury transit, now-a-days, has no scientific significance as such but certainly helps generate scientific awareness amongst youngsters and elders alike," Nehru Planetarium Director N Rathnasree told reporters.

The whole exercise at the planetorium was a sort of a dry run ahead of the Venus transit next year, when detailed observations will be made to calculate accurately the distance of the Earth from the Sun, also known as the Astronomical Unit (AU), Rathnasree said.

As predicted, planet Mercury made the first contact with the Sun exactly at 10:42 hours on the North Eastern region. It then took a leisurely five hours 13 minutes before leaving the Sun-dial at 16:01 hours from the North Western region.

"The larger size of Venus, which is less distant from the Earth when compared to Mercury allows us to calculate the AU more accurately, Chander Devgun of the Amateur Astronomers Association (AAA), Delhi told reporters.

A rare celestial event, Mercury transits take place just 13 times in hundred years and was used in the late 17th century by astronomers to calculate for the first time the distance between the Sun and the Earth.

Nehru Planetarium in association with AAA had made elaborate arrangement for telescopes, live telecast and webcast of the transit, Rathnasree said adding, a special website for live feeds too attracted good traffic.

PTI