Venus is the black dot seen on the Sun, June 8th 2004. A transit occurs when Venus passes in front of the Sun as seen from Earth. This is the first transit since 1882. Venus is an Earth-sized planet that orbits in between Earth and the Sun. It does not appear to cross the Sun's disc during every orbit as the orbital paths of the Earth and Venus are not in exactly the same plane. Venus transits occur in pairs separated by eight years, with alternating intervals of 121.5 and 104.5 years in between pairs. Only Mercury and Venus can transit the Sun as seen from Earth.