The transit of Venus across the face of the sun will soon take place.
The event has not been witnessed in the last 122 years.
"No human alive has seen this phenomenon," a Nehru Planetarium official said, adding that on June 8, 2004, Venus will drift across the face of the sun, as it passes between sun and the earth.
It is a rare alignment. Indeed, only six such events have occurred since the invention of the telescope-- in 1631, 1639, 1761, 1769, 1874 and 1882.
The next two will occur on June 8, 2004 and June 6, 2012.
"Simple as transits may seem, they are instrumental in defining our place in the cosmos and historically speaking, expeditions were launched at these times to quantify the size of the solar system," according to planetarium Director Piyush Pande.