Planetarium coordinator to speak on transit of Venus

What happens when the planet Venus passes, or transits, directly between the sun and Earth, becoming visible against the sun?

Ric Alling, ASU planetarium coordinator, will speak on “The Transit of Venus Through the Ages” during a free lecture at 7 p.m., April 13, in Bateman Physical Sciences Center F-173, Tempe campus.

“We will briefly look at the phenomena of Venus' transits of the sun from the perspective of orbital mechanics, then we will look at the historic events that followed the development of astronomy and the history of transit observations,” Alling said.

Transits of Venus occur in a pattern that repeats every 243 years, with pairs of transits eight years apart separated by long gaps of 121.5 years and 105.5 years. The next transit will be on June 6, 2012.

Telescopes will be set up after the lecture for sky viewing. For more information about the lecture and future astronomy events at ASU, go to