On Tuesday, June 5, Venus will move across the face of the sun in an event called the Transit of Venus. Scientists call it is the rarest predictable astronomical event, happening only four times every 234 years!
The last time this event occurred was on June 8, 2004 and was watched by millions of people across the world. On June 5, Venus will make its final trek across the face of the sun until the year 2117, so this will be your only chance to see it live!
To celebrate, NASA is hosting a live webcasts of the event from around the world. For more info on the webcasts click here: http://sunearthday.nasa.gov/2012/transit/webcast.php
Check out the video below to see what Venus looked like as it passed across the sun in 2004.