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Transit of Venus: Scientists hope to learn from rare event

June 5, 2012 | 11:45 am

Click for full coverage of the transit of VenusWhile the Transit of Venus is generating public excitement, there is special interest from experts who hope they can learn from the rare event.

Jean-Michel Désert, a  Harvard University researcher, will take part in a nearly 400-year-old astronomical obsession — tracking Venus as its orbit carries it directly between Earth and the sun.

This rare event, known as a transit of Venus, takes place only once every century or so, usually in pairs spaced eight years apart. The next one won't happen until Dec. 11, 2117.

FULL COVERAGE: Transit of Venus

"This is a great opportunity for us," Désert said.

"This is a new century, and there's a new set of astronomical questions for which the transit can prove important," added Jay Pasachoff, an astronomer at Williams College in Williamstown, Mass. "With telescopes on the ground and in space, we can now use the transits to study things that had not been conceived of in the past."

Pasachoff has been lobbying his fellow astronomers to take the transit seriously, writing last month in the journal Nature that squandering the opportunity to collect as much data as possible would be "a crime."

Pasachoff is in position at the University of Hawaii's Mees Solar Observatory on the summit of Haleakala to observe the transit in its entirety and assess how the Venusian atmosphere polarizes sunlight. Astronomers on his team will be positioned around the world to take measurements with coronagraphs, spectrographs and the orbiting Solar Dynamics Observatory.

Even scientists with no professional stake in the event said they would watch the skies Tuesday because the whole thing is just plain neat.

"I think for most of us there's a connection to the science we do, but it's mostly an opportunity to watch a rare and cool event," said Caltech astronomer Heather Knutson, who studies exoplanets. "That's why many of us went into the field in the first place."

To watch the sun safely means viewing the show through a solar filter. The best view is through a magnified image of the sun – and that means through a filtered telescope. In Southern California, the Griffith Observatory at Griffith Park in Los Angeles, Columbia Memorial Space Center in Downey and UCLA Planetarium will offer free access to outfitted telescopes.

Venus will cross its midpoint on the sun’s disc around 6:25 p.m. PDT. In the continental United States, the show will end at sunset, but Venus will continue to be visible on the sun’s disc until roughly 10 p.m. PDT westward. That means places like Alaska, Hawaii, Asia, Australia, eastern Africa and all but the western edge of Europe will get to see the planet exit the sun’s disc.

You can also buy special solar eclipse glasses that can be used to look directly at the sun safely, blocking at least all but 0.003% of visible sunlight. They’re still available at the Griffith Observatory gift shop for $2.99 a pair. A bargain deal, with pairs selling for just 85 cents, can be found at a wholesaler that manufactures them, Rainbow Symphony at 6860 Canby Ave., Suite 120, in Reseda. It will be open between 8:30 a.m. and 5:30 p.m. Tuesday.

Transits of Venus have not been known to humans for very long. The theory behind the transit goes back to the 17th century, when German astronomer Johannes Kepler predicted that both Mercury and Venus would cross over the Sun’s disc from Earth’s viewpoint. But Kepler’s prediction of a transit in 1631 was disappointing in that it wasn’t visible in Europe during that year.

So the credit to the person who first predicted –- and observed –- the Transit of Venus goes to an English astronomer, Jeremiah Horrocks, which he did in 1639.

It wasn’t long before scientists realized there would be more transits in the future, and there were: in 1761, 1769, 1874, 1882, 2004 and 2012.

Able to photograph the transit? Tweet it to us at @LANow and tag it with #LAVenus. You can upload photos to our website.


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-- Rong-Gong Lin II, Eryn Brown and Amina Khan