Watch the 'Transit of Venus' on Tuesday

Unless you plan to be around in 2117, you may not want to miss this upcoming astronomical phenomenon.

On Tuesday, June 5, the planet of Venus will cross the sun and will be visible from a large portion of the United States.

observatory and NASA Ames will have free viewings, open to the public.

"The Venus Transit is indeed a rare event, and full of historical lore," says the website of the Peninsula Astronomical Society, which will be running the Foothill viewing that begins at 3:30 p.m. and ends at 7 p.m. 

NASA Ames invites the public to watch a live broadcast at 3:04 p.m. from the Exploration Center as Venus first makes its appearance in Mauna Kea, Hawaii.

For several hours, viewers will see Venus as a small dot drifting across the sun. There have only been 53 transits since 2000 B.C. The last occurance took place on June 8, 2004.

The Venus transit will be the last opportunity to witness the rare astronomical event until 2117. Such transits come in pairs every 120 years, with the pair spaced eight years apart.

"The first event of the current pair ... was not visible from California," read the announcement from the Peninsula Astronomical Society. "Hence, this final event is truly a once-in-a-lifetime event for Californians."

At NASA Ames, attendees will have an opportunity—2-8 p.m.—to participate in hands-on activities and safely view the transit of Venus through solar filter glasses and telescopes.

The transit, first recorded by English astronomer Jeremiah Horrocks in 1639, has also been observed by Captain James Cook in 1769. Cook gathered transit data from various locations around the world that used to calculate the distance between Earth and the sun and the size of the solar system.

"Prominent astronomers in the past used Venus Transits as a means to measure the Astronomical Unit, a holy grail for astronomy in the Eighteenth and Nineteenth centuries," the PAS site said.
 
Today, transit events are used to detect planets beyond the solar system. measures the change in brightness from distant stars when a planet passes in front of the star. Kepler has confirmed 61 planets and more than 2,300 planet candidates using the transit technique.
 
The NASA Ames Exploration Center is the large white dome located at the main gate of NASA's Ames Research Center. To reach NASA Ames, take U.S. Highway 101 to the Moffett Field, NASA Parkway exit and drive east on Moffett Boulevard towards the main gate and bear right into the parking lot.

For more information about the worldwide events, safety precautions for viewing, educational content and social media activities, visit:
http://venustransit.nasa.gov

The public can follow the event on Twitter on #VenusTransit and download a free mobile app at: http://venustransit.nasa.gov/2012/multimedia/apps.php