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Today's the day: Look up to see the last transit of Venus this century

Ben Anderson

Alaska may have missed out on the prime viewing of the annular solar eclipse on May 20 -- though it definitely caught some of it -- but there's no better place to be than the Last Frontier to see Tuesday's transit of Venus, an astronomical event that only rolls around twice every century or so.

The transit of Venus is a seven-hour event in which Venus -- one of only two planets between the Earth and its heavenly light -- treks its way across the surface of the sun, beginning about 2 p.m. The transits come in groups of two, set eight years apart, but then don't occur for more than another century.

The last one occurred in 2004, making the June 5 event the last one until 2117. Before 2004, the last one was in 1882.

So unless modern medicine makes immense strides soon, this year's event will be the only chance living Earthlings will have to see it.

But here's the catch: Just like the recent solar eclipse, the best viewing will be in limited geographic regions. The Los Angeles Times reports the transit "will be visible in its entirety only from the western Pacific, eastern Asia, eastern Australia and at high northern latitudes."

High northern latitudes, you say? Sounds like Alaska, no?

Yes, but will the weather cooperate? The National Weather Service is calling for partly cloudy skies Tuesday in Anchorage. If not perfect, Fairbanks sounded a tad better. Alaska's second-largest city is expecting partly sunny skies with scattered showers. 

If the skies are clear, the 49th state will be among the prime viewing locations -- so much so, that many astronomers and space enthusiasts planned to travel Fairbanks to facilitate viewing. That's according to Space.com, which said a group of researchers from NASA's Solar Dynamics Observatory was planning a trip north in concert with a solar physics meeting in Anchorage.

Also planning to come up for the transit is a group of researchers from the University of North Dakota Sun Earth Moon Systems team, who will feature a live webcast of the transit on their site.

According to Tim Young, an associate professor of astrophysics at UND, the group will be setting up for a public-viewing event at the parking garage on the University of Alaska Anchorage campus behind the Conoco Phillips Integrated Science Building. To help fund the trip to Alaska, they'll be selling glasses designed for viewing the transit for $2.50. Three weeks ago, they webcast the solar eclipse from Redding, Calif.

They were planning to travel elsewhere if the weather wasn't cooperating, but Young said Monday that the forecast looked good enough to merit sticking around.

Alaska and Hawaii are the only U.S. states that will see the entire transit, which is different than the 2004 eclipse, when the western U.S. missed the entire show, according to NASA. Parts of eastern Australia and Asia will also see the entire transit.

That's not the transit's only Alaska connection, either. According to MSNBC, British explorer James Cook -- for whom Alaska's Cook Inlet is named, and who mapped a good portion of the Alaska coastline during a quest to discover the fabled Northwest Passage -- assisted in a scientific expedition during the 1769 transit of Venus.

The goal was to answer one of astronomy's most important questions -- the distance from Earth to the sun. By precisely timing the transit's length from many different points around the globe, the reasoning went, scientists could calculate the Earth-sun distance using the principles of parallax. With this information in hand, the scale of the entire solar system would follow.

Famed British explorer Capt. James Cook took part in the 1769 expedition, sailing to Tahiti and watching the transit from a place now known as Point Venus.

Tim Young with the University of North Dakota said that although radar has allowed for highly accurate measurement of the Earth's distance from the sun, scientists will attempt to replicate the techniques used in previous transits for comparison purposes.

"It is of interest to do the same calculation with very simple techniques and equipment and see if it is possible to get a good estimate from what they attempted in 1874 and 1882," Young said.

In Fairbanks, where the skies look a bit more promising, NASA is planning a webcast in conjunction with the Fairbanks Astronomical Unit and the National Institute of Aerospace. You can see more details on that public viewing event at this website. There will be hands-on activities and viewing opportunities if the sun peeks through the clouds.

NASA will also broadcast the whole event on its NASA TV website. Fair warning: You won't be able to look directly at the sun to view the transit, but need to filter it through some sort of medium. Tips for viewing solar eclipses apply.

In Anchorage, the transit will begin at about 2 p.m. and end around 9 p.m. Curious what times it will be visible in your area? Check out this handy site. Will the weather cooperate in your corner of the state? See the forecast for your region at the National Weather Service.

Contact Ben Anderson at ben(at)alaskadispatch.com