After a gap of about ten years, transit of Mercury over the disc of the sun will take place in the afternoon of May 9 and will be visible from India. Mercury will surpass the Sun at about 4:30 pm, revealed Astronomical Society of India (ASI). Solar system's smallest planet will take a couple of hours to cover the quarter of its path. After 6:30 pm IST, people in India will not be able to see the remaining transit due to the sunset.

Astronomers and space enthusiast are excited to witness the stunning transit. Next Mercury’s flyby will occur in November 2019, but will not be visible from India. The rare Mercury transit will be visible from nearly all parts of the Earth including: Europe, Asia, Africa, North America, South America, Pacific, Atlantic, Indian Ocean, Arctic, Antarctica. However, it will not be visible in Japan and other parts of eastern Asia. It will not be visible in Japan and other parts of eastern Asia.

Indian observers said that the Mercury will move from the ‘top’ towards the ‘bottom’ of the Sun while moving towards the western horizon. Mercury transit is a very rare phenomenon and it will occur 14 times in the 21st century.

The transit of Mercury is a phenomenon in which, the planet will be seen as a small black dot travelling from one end of the solar disc to the other, said Sanjib Sen, Director, Positional Astronomy Centre. This phenomenon is seen when the Mercury passes between the sun and the earth and it happens only when the three are lined up, Sen said.

The transit of Mercury begins with contact-I, the instant when the disc of Mercury is externally tangent with the sun (ingress exterior) followed by contact-II, when Mercury is internally tangent with the Sun (ingress interior). Mercury will be seen as a black spot, travelling several hours over the face of the disc and will reach the opposite limb of the sun at contact-III, when the disc of Mercury is internally tangent with the sun (Egress interior). The transit ends at contact-IV when the disc of Mercury is externally tangent with the sun (egress exterior).

By Premji