Public Invited to View ‘Transit of Venus’

Stephen Karl views the 2006 Mercury transit using a 10-inch telescope. Photo: Patrick O’Donnell Download Photo

Q&A With Stephen Karl

Stephen Karl has been waiting nearly two decades for the “Transit of Venus.” 

“I became aware of this transit about 20 years ago — and I have been waiting ever since,” said Karl, staff microscopist in the university’s Biological Science Department.

As a microscopist, Karl prepares specimens and takes pictures of them with a microscope, but for this event, he will use telescopes, in which different types will be available for public viewing.

Viewing of the transit is dependent on clear skies, Karl explained. The transit, however, will continue until after sunset. “So people looking at the setting sun will be able to see Venus without any aids during sunset. However, June is notorious for being overcast at sunset, especially at the beach.”

What is the significance of the transit?

The transit of Venus has only historical significance. During the 17th century, astronomers determined how all the planets moved about the sky. They had determined all the distances from each planet to the sun, the size of the planets and their relative velocities. But all the values were relative to “astronomical units,” or the distance from the Earth to the sun.  For example, the distance of Venus to the sun would be 0.72 AU. The size of Venus was 58 Arc seconds. There were no hard values at the time because the actual distance from the Earth to the sun was unknown. Astronomer Edmond Halley (of Halley’s comet fame), among others, realized that by observing Venus transiting across the sun from different points on the Earth, they could triangulate the real distance to the sun, and all the other values would fall into place. The only problem is the transit only happens every 100 years or so, which they had years to plan. This was also why Captain Cook took his famous voyage of the “Endeavour” to Tahiti. He along with many others ventured to various spots in the world to make one observation. It was considered at the time to be the largest scientific undertaking in history.

Why is this transit worth viewing?

It will be the only time we will be able to see Venus transit in our lifetime. The next transit won’t be until 2117. Also, since Venus will be closest to the Earth during the transit, it will appear larger than any other planets in the solar system.

What will people see — with or without telescopes?

Most importantly, do not look directly at the sun. But if you use a pair of solar viewing glasses, available at the event, or view with a telescope equipped for solar viewing, Venus will appear as a black disc against the sun and appear to be larger than any other planet. Darker regions on the sun, called sunspots, also will be visible. In addition, we will have a large H-alpha solar telescope, in which people will be able to see the solar flares on the sun as Venus transits.

What are other highlights at the event?

Joshua Smith, assistant professor of physics, and I will give lectures about the history of the transit and about the sun, Venus and the “runaway greenhouse effect” that makes Venus the hottest planet in the solar system. There will be a scaled two-dimensional planet walk, which shows the size and position of the planets at the time of the transit and participants will be challenged, by using celestial charts, to find all the ‘planets’ placed in the Arboretum and on campus. Those that find all the ‘planets’ get a free pair of solar viewing glasses.

There will be physics demonstrations  and astronomers from the College of Natural Sciences and Mathematics will answer questions.