Live: Watching for Venus to Cross the Sun . ... Credit Copyright: NASA / SDO the AIA, EVE, and HMI teams Explanation: Today Venus moves in front of the Sun. One way to follow this rare event is to actively reload the above live image of the Sun during the right time interval and look for an unusual circular dark dot. ... This transit is the rarest type of solar eclipse known -- much more rare than an eclipse of the Sun by the Moon or even by the planet Mercury . ... NASA Official: Jay Norris. ...