Venus transit app allows viewers to follow planet's passage across sun

Today you will have a chance to catch one of the rarest celestial events viewable from Earth.

The planet Venus will make a trek across the sun. This phenomenon has only been observed six times in recorded history.

Another occurrence won’t happen until 2117. The eclipse of Venus will start around 6 Tuesday night, the planet will pass between Earth and the sun.

There's also an app for the event. You can even help scientists record Venus' voyage by using the Venus transit app.

The app comes with a built-in timer to calculate how long Venus takes to cross the sun. It also has simulation and visibility sections to tell users when the transit will begin.

It's based on their GPS coordinates. Once Venus has made its trek, all of the data from users tracking it will be sent to central servers to be compiled.