University of South Carolina

Transit of Venus is Tuesday evening your next chance to see it will be in 105 years

By Steven Powell,, 803-777-1923

USC is preparing to showcase one of the rarest of astronomical events on Tuesday, June 5. If you can't catch the Venus transit of the sun then, you'll need an extended calendar to mark the next opportunity: December 2117.

But for those who would rather not wait more than a century, the staff of the Melton Memorial Observatory is holding a special observation session in the Wardlaw College parking lot Tuesday, starting at 5 p.m. In addition, the Ernest F. Hollings Special Collections Library has mounted an exhibit that chronicles the history surrounding the event.

"The Venus transit begins at about 6:05 p.m., but we're planning to set up in the Wardlaw lot earlier, at 5 p.m., and we'll be observing the sun until sundown, which is about 8:30 p.m.," said Alex Mowery, director of the observatory. "The transit actually continues until after midnight, but from this part of the globe we'll only be able to see the first few hours of it because the sun will go below the horizon."

The transit of Venus is the movement of Venus across the disk of the sun. Venus orbits closer to the sun than earth, and on rare occasions the planet lines up directly between the sun and the earth. In principle, it's similar to a solar eclipse, in which the moon lines up between the earth and sun.

The primary difference is how much of the sun each obscures. Venus is much larger than the moon, but also much further away. So while the moon can totally obscure the sun (a total eclipse), a transit of Venus looks like a small black disk moving across the sun over the course of several hours.

The trick is to be able to view it safely, because permanent blindness can result from improperly observing the sun. "It's not safe to watch it with the naked eye," Mowery said. "We've ordered 25 pairs of glasses that you can use to safely watch the transit, and we'll have telescopes set up with filters for safe viewing."

"Our camera will be transmitting the whole event, too, and if you go to our website you can watch the whole thing," said Mowery. "We're also planning to stay later than sundown and look at Mars and Saturn from the Wardlaw parking lot."

The first recorded observation of the transit of Venus was in Persia in 1032. In the 17th century, astronomers became interested in observing the event because careful measurements would allow the calculation of the distance from the earth to the sun.

Since then, a range of monographs have detailed this exceedingly rare occurrence. Some of the selected books on display in the Hollings Library in “The Transit of Venus in Books from the Irvin Department of Rare Books and Special Collections” detail and predict transits centuries into the future. These rare 18th- and 19th-century volumes are from the Robert B. Ariail Collection of Historical Astronomy.

Among the items on display are Johann Gabriel Doppelmayr’s “Atlas Coelestis” (1742), in which he predicts the transit of Venus on June 6, 1761, in a diagram, and “Transits of Venus,” a book written by popular astronomer Richard A. Proctor around the time of the 1874 transit that included sketches of what the 2004 and 2012 transits would look like.

“An Account of the Voyages Undertaken by the Order of His Present Majesty for Making Discoveries in the Southern Hemisphere,” published in 1773, includes Captain James Cook’s extensive account of first building an observatory to view the coming transit in 1769 and, a few pages later, a succinct and very different entry about the same event by botanist Joseph Banks.

More contemporary books, including Andrea Wulf’s just-released “Chasing Venus: The Race to Measure the Heavens,” are also part of the exhibit.

The exhibit is open 8:30 a.m. to 5 p.m., weekdays in the Hollings Library, which is accessible through Thomas Cooper Library.

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Posted: 06/01/12 @ 2:45 PM | Updated: 06/01/12 @ 3:40 PM | Permalink