Visitors to the Arboretum at the University of Kentucky on Tuesday took advantage of a rare opportunity to see Venus move across the face of the sun.
One of the rarest astronomical events, the transit of Venus, occurs when Venus passes between Earth and the sun. It won't happen again until December 2117.
The transit allowed people around the world to observe the planet as a small black dot crossing the sun. The Arboretum hosted a public viewing that drew about 200 people, who took turns looking through telescopes with special filters between periods of cloud cover.
Tuesday's celestial event was only the seventh of its kind since 1639. Tim Knauer, director of the University of Kentucky observatory, said past astronomical events have generated a lot of public interest. "When something in the daytime sky changes, it's always intriguing," Knauer said. Observers at the Arboretum agreed.
"It's all about the opportunity to see something that we will never get to see again," Kathy Simon said.
"It's incredible," Joe Brewer said after looking through the telescope. "It's important that my daughters were able to see it and we were able to come together for an event that only happens once in our lifetime."
Knauer said the transit couldn't be seen without the aid of a telescope.
He said the event is of limited scientific purpose now, but a similar event centuries ago helped astronomers determine the distance from the Earth to the sun.
In 2006, a group of astronomers used the transit of Mercury to measure the precise size of the sun. The transit of Mercury happens much more frequently and is observable as a smaller dot.
This year's transit of Venus might help astronomers hunt for planets outside the solar system, Knauer said.