On Tuesday, the planet Venus will pass between Earth and the Sun, appearing to cross the face of our star in a rare event known as a "transit." The next transit of Venus to be visible from Earth won't happen until December 2117. In other words: you don't want to miss this. Here's everything you need to know to catch a glimpse.
What is a Transit?
"Transit" is just the word astronomers use to describe one cosmic body passing in front of another from a third object's perspective. Two weeks ago, the Moon made a transit of the Sun, crossing between our star and the Earth in an annular eclipse. When scientists scan the Milky Way for planets outside our solar system using the Kepler telescope, they generally do so via the "transit method" (depicted here), detecting planets by looking for dips in the brightness of a distant star that occur when an orbiting planet passes between it and Kepler's line of sight.