CEDAR FALLS, Iowa – Iowans will witness a rare event on June 5, when the planet Venus transits the sun. The last transit of Venus occurred on June 8, 2004, according to Siobahn Morgan, head of the Department of Earth Science at the University of Northern Iowa, and the next one will not occur until Dec. 11, 2117.
If the weather is clear, solar viewing equipment will be available for the public to safely view the transit starting at 5 p.m., Tuesday, June 5, near the parking lot to the west of the UNI-Dome, near the athletic fields.
A transit is similar to an eclipse, with the various objects involved in the event all lined up. Although most or all of the sun is blocked by the moon in a solar eclipse, the planets Mercury and Venus appear as small objects in the sky because they are so far away, Morgan explained. Thus, these planets are unable to cover very much of the sun's disk. "As we view it, the sun would appear to be about 32 times wider than Venus during the transit," she said. Even so, with the proper equipment, observers will be able to see Venus easily.
Viewing the sun for extended periods of time should only be done with proper solar filters, Morgan stressed. "People should never look at the sun with binoculars or telescopes that aren't outfitted with the appropriate solar filters. Even a small amount of unfiltered sunlight seen through a telescope will damage your eyes," said Morgan.
The transit of Venus across the sun is a much slower process than the recent eclipse, in part because of the distance of the objects from Earth and their relative velocities. For observers in Iowa, Venus will begin to move in front of the sun around 5:05 p.m., and continue to progress slowly across the northern area of the sun's disk. The entire passage of Venus across the sun will not be visible to those in Iowa because the sun will set before the end of the transit. People in Hawaii, Alaska and the far western Pacific area will be able to see the transit in its entirety, which lasts more than 6.5 hours.
The viewing is free and open to the public. For more information, contact Morgan at 319-273-2389 or firstname.lastname@example.org.