Observatory to mark Transit of Venus

Stargazers on campus will have a front-row seat to a cosmic event in early June.

A photo of the SF State observatory.

The SF State observatory will hold a viewing of the Transit of Venus on June 5.

The University's observatory will host a viewing of the Transit of Venus, the passing of the planet Venus between the Earth and the sun. The event happens twice -- in pairs eight years apart -- every 120 years. The Transit of Venus taking place June 5 is the second of the most recent pair, meaning another one will not happen again until next century.

"This is your one shot to see the transit," said Professor of Physics and Astronomy Adrienne Cool. "One chance in this human lifetime."

The observatory's equipment will be set up to allow members of the public to view the transit, and a camera will be attached to a telescope with a solar filter to capture images of Venus passing in front of the sun. The transit can be seen with the naked eye and solar viewing glasses, and sun spotters will be on hand for attendees to use, since looking directly at the sun can cause permanent damage to the eyes.

The Transit of Venus has both historical and modern significance, Cool said. First observed in 1639, astronomers realized they could measure the solar system by timing the transit from various locations on Earth, comparing differences in timing at those locations to measure the distance of Venus and Earth from the sun, and then applying those measurements to already-known relative distances of the planets. Attempts to take measurements in the late 1700s -- including an expedition to Tahiti by famed captain James Cook -- failed to obtain accurate readings, but successful measurements were taken the next time around in the late 1800s.

"One of the benefits of viewing the transit is creating that connection to astronomers of yore and adventurers of yore," Cool said.

In modern astronomy, the Transit of Venus mimics one of the ways new, faraway planets are detected: through a temporary dimming of light as the planet passes in front of its home star.

During the transit, Venus will appear as a small, perfect black circle passing slowly in front of the sun.

"It instantaneously gives you this sense of scale," Cool said. "Venus is about the size of the Earth, and we're going to see it as this tiny dot crossing the sun. It's humbling and fun to see that directly."

The transit will begin at 3:06 p.m. on June 5 and lasts about six and a half hours. The sun will set in San Francisco before Venus has finished its path across the sun. The observatory will hold its viewing weather-permitting and anyone interested in attending should call the observatory at (415) 338-7707 or visit its Facebook page the morning of June 5 to confirm the event will take place. The observatory holds about 15 people and additional viewing locations will be set up outside Thornton Hall.

The observatory can be reached by taking the elevator in Thornton Hall to the ninth floor, then following the signs. For more information about the observatory, visithttp://www.physics.sfsu.edu/astronomy/observatory.

-- Jonathan Morales