KNAU and Arizona News
9:09 am
Tue June 5, 2012

Transit of Venus Graces The Skies Over Flagstaff

Over the last few weeks, northern Arizonans have witnessed a lot of astronomical drama: the annular eclipse earlier this month and a partial lunar eclipse yesterday. Today. Flagstaff will have one of the most impressive views of the Transit of Venus. It's a rare event that happens when Venus passes between the sun and the Earth. And, as Arizona Public Radio's Gillian Ferris Kohl reports, it's an event most of us will never see again.

Astronomers from all over the world are milling around the grounds of Lowell Observatory in Flagstaff. They're looking for the perfect place to set up their telescopes to watch Venus travel between us and the sun. Paolo Tanga has found his spot.

"I came here from Nice with two instruments we built for this. As far as I know these are the only instruments that have been built for this opportunity to see this event and they are so rarely visible that this is fascinating...exciting!"

Transits of Venus happen about every 115 years. They occur in pairs, generally about 8 years apart. The last one was in 2004.

"Anyone that even has a remote inkling to have bragging rights to tell their grandchildren or great grandchildren should see this one because you won't have another chance."

Bill Sheehan is an astronomy historian and author. He also happens to be in love with Venus.

"Venus is one of the most beautiful objects in the night sky. It's been an object of fascination since very early times. And it was worshipped by the ancients as a goddess, part of the celestial triad with the sun and the moon."

But, Sheehan says the scientific data gathered from these rare events is  even more amazing.

"It was during a Transit of Venus that Venus's atmosphere was first discovered. So, it was really necessary to get some sort of measure of the scale of just how bit the solar system was."

And, Sheehan says the data has also been invaluable in finding planets in other solar systems. None of this research would be possible if not for a telescope designed by the famed Alvan Clark and his sons. It was used to observe the Transits of Venus in 1874 in Siberia and in 1882 in Texas. The scope is now kept at the US Naval Observatory in Flagstaff. Telescope engineer Mike Divittorio has been busy refurbishing it for today's event.

"So, what you're looking at is a brass tube, it's about six feet long. At one end is a cell that holds the main lens. We were able to mount the focuser without changing the tube. It's a very delicate instrument, but it's ready to use now and the public will be able to look through it with a solar filter, of course."

Normally, the Naval Observatory is open only once a year to the public, during the Festival of Science. But, Divittorio says today they're making an exception. The grounds will open at 3 and visitors will be able to look through a century old telescope at a celestial event that won't happen again until 2117.

For Arizona Public Radio, I'm Gillian Ferris Kohl, in Flagstaff.