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Steve Chaplin
IU Communications

Last modified: Thursday, May 31, 2012

IU Astronomy will host viewing of Venus crossing the sun, a once-a-century astronomical oddity

Solar-filtered telescopes will be placed atop Henderson garage for public event

May 31, 2012

BLOOMINGTON, Ind. -- Almost no one living today will be around to see the next one in 105 years, so the transit of Venus across the sun on Tuesday, June 5, is a once-a-century event that Indiana University's Department of Astronomy wants to be sure no one in Bloomington misses.

In this photo from NASA, Venus can be seen in the lower-right corner as a dark circle moving across the face of the sun.

The rare astronomical oddity will next occur in 2117, so astronomy faculty, staff and students will create a regular tourist event from atop IU's Henderson Parking Garage, complete with solar-filtered 8-inch telescopes and ultra-dark glasses to allow guests to view what will be about a seven-hour event.

The transits occur in pairs about eight years apart, with the most recent one viewable in the east at sunrise in 2004. Astronomy professor Caty Pilachowski said that viewing event on the top deck of the Atwater Garage was a big success and that the department has been hearing from people about a viewing for the June 5 transit that will be seen in western skies beginning around 6 p.m. The previous pair of transits occurred in 1874 and 1882, and the next pair won't occur until 2117 and 2125.

"We had a large crowd turn out in 2004, and we're already getting calls from people asking what we are going to do for this upcoming transit," she said. "We'll be watching as long as the sun is up in the evening, and the whole event lasts nearly seven hours."

Astronomer and mathematician Johannes Kepler in 1627 was the first to predict that Venus would pass between Earth and the sun. In 1716, Edmund Halley, of Halley's Comet fame, determined one could compute the distance of the Earth from the sun during the transit. By the time of the 1761 and 1769 transits, scientists calculated that distance at 95 million miles. In 1896, Simon Newcomb's value -- a distance from Earth to sun of 92,702,000 plus or minus 53,700 miles -- was adopted by the international scientific community. Today most textbooks report the Astronomical Unit (or AU) as 93 million miles.

"We had good luck with the weather in 2004 and hope for the same this time," Pilachowski said. "We've also created a Web page for the event, and for those who can't make it, there is a live webcast of the transit available from the Mauna Kea Observatories."

The live webcast from Mauna Kea will begin at 5:45 p.m. EST.

The Henderson Garage is on Fess Avenue between Atwater Avenue and Third Street, with for-pay parking available in the garage through entrances on Fess and Indiana avenues.

Pilachowski did offer one admonition for transit viewers: take the usual precautions for viewing solar events.

"You should be careful never to look directly at the sun and never to look at the sun with binoculars. Viewers should use only approved devices to see the transit, and simple pinhole projectors can be made at home from instructions on the Web," she said.

Those instructions include using a pinhole or binoculars to project the sun onto a sheet of paper.

For more information, contact Steve Chaplin, Indiana University Communications, at 812-856-1896 or Tweeting Indiana University science news: @IndianaScience. Subscribe to the Indiana Science news blog, Science at Work.