Bangalore: In a rare celestial event, planet Mercury will pass in front of the Sun as viewed from earth on May 7.

On an average, there are 13 such transits of Mercury in a Century and the event would be visible from India between 10.43 am (IST) to 4.00 pm (IST) on May 7, an Indian Institute of Astrophysics (IIA) release said.

"Though not as exciting as a solar eclipse or a comet, this event is of interest in its own right. It is very difficult to observe as the planet is small (2,438 km mean radius compared to 6,95,950 km of the Sun) and will appear as a very small dot against the bright disc of the Sun. It will be virtually indistinguishable from a sunspot," IIA said.

The institute has asked people to use adequate filters before viewing the celestial event from a telescope.

Transits of only Mercury and Venus are visible from Earth and the transit of Venus, which is bigger is rarer.

"Interestingly, there is a transit of Venus due on June 8, 2004 and it will be visible from India," it said.

PTI