In a rare astronomical phenomenon, planet Mercury will be seen as small black dot on the solar disc from several parts of India on Monday; the dot will be travelling from one limb of the solar disc to the other. This astronomical phenomenon is very rare as it occurs only 13 times in a century and it occurs only when the Sun, Mercury and the Earth are lined up in one plane and the planet appears as a dot on the disc because its angular size is very small compared to that of the Sun as seen from the Earth.