WEBCAST OF THE JUNE 5, 2012 Transit of Venus

On June 5, 2012, the Exploratorium webcast the 6.5-hour transit of Venus live from the Mauna Loa Observatory in Hawaii.

Video clips showing the beginning (1st and 2nd contact) and end (3rd and 4th contact) of the transit, as well as a highlights clip that includes sunspots and solar prominences, are now viewable here.

The videos show the transit through three different telescopes. The yellow- looking sun was imaged through a white-light telescope, filtered only to decrease the sun's brightness. The violet-hued sun is the result of a calcium filter. Calcium ions emit wavelengths in the ultraviolet part of the spectrum, which the camera interprets for us. The red-colored sun was shot through a hydrogen-alpha filter, which only allows red light emitted by hydrogen to reach the camera.

As the video signal was received at the museum, Exploratorium composer Wayne Grim converted it into a sound composition .

What Is a Transit of Venus?

Transits of Venus—the movement of Venus across the face of the Sun—occur in pairs that are eight years apart and then don’t happen again for more than a century. Prior to the current pair, the last two Venus transits were in 1874 and 1882. After the transit in 2012, there won’t be another pair until 2117 and 2125. These rare alignments have been important for scientific research. Of particular significance, Venus transits provided observers with data that eventually led to a very close estimate of the astronomical unit —the distance between the earth and the sun. (See 1761 and 1769 on the timeline and Why Is It Important? ) Browse the timeline to learn some of the history of Venus transits along with related scientific ideas and breakthroughs.

2004 Transit, June 8
The Exploratorium sent a crew to Greece to webcast the transit. View the webcast archives and still photos from 2004.

Mauna Loa Observatory

The Exploratorium webcast the transit of Venus from Hawaii’s Mauna Loa Observatory (MLO), which is located on the north slope of the Mauna Loa volcano at an elevation of more that 11,000 feet (almost 3400 meters)... more