Total Solar Eclipse 2012: Taking The Sun's Temperature

on November 12 2012 3:18 PM

A total eclipse in Australia on Tuesday will provide both amateur and professional astronomers with a visual feast – and help scientists study the mysteries of sun's fiery upper atmosphere.

On November 13, at 3:35 p.m. Eastern Time – just after dawn on Nov. 14 in Australia – the moon will pass between the sun and the Earth, completely blocking the solar disc. If you can't manage to get "down under" to view the eclipse, organizations like the Slooh Space Camera and Australian tourism agencies will be livestreaming the celestial event.

Scientists will be watching the eclipse with instruments to get a better understanding of why the sun's corona, or outer atmosphere, is so hot – 1,000,000 degrees Celsius (1,800,032 degrees Fahrenheit) to the relatively balmy 6000 degrees Celsius (10,832 degrees Fahrenheit) on the sun's surface. While researchers have instruments that can monitor the suns corona, the moon reveals the corona's secrets far better than anything manmade.

As the moon passes between the Earth and the sun, it “reveals the innermost corona, which manmade coronagraphs have trouble seeing,” Shadia Habbal of the Institute for Astronomy in Hawaii told NASA's news service. “That is where all the magnetic field and physical processes responsible for heating the corona are evolving most rapidly."

The fact that we can view solar eclipses at all is due to several serendipitously aligning arrangements of astrophysics. Thanks to the tidal forces between the Earth and the moon, the moon gets pushed out incrementally further. The orbit moves out just about 3.8 centimeters (1.5 inches) every year, but over the millenia that can add up.

Hundreds of millions of years ago, our moon was closer to us, making its disc appear much bigger than the sun's as it passed over. A billion years from now, the distance between the Earth and the moon will have increased by nearly 24,000 kilometers (15,000 miles), making the moon appear smaller and more easily swallowed up by the sun.

Fortunately, there's plenty of solar eclipses between now and 1.4 billion years from now, when scientists predict the last total solar eclipse on Earth ever will occur.

There are 68 total solar eclipses that have already occurred or will occur this century. The last total solar eclipse in July 2010 was best viewed from southern Chile and Argentina, as well as parts of Polynesia. The next total solar eclipse will come in March 2015, though that will only be visible from islands in the North Atlantic and Arctic, with bits of Europe and Central Asia getting a partial view. Americans won't get a good view of a total solar eclipse until August 2017.

For now, scientists will use the data gathered from the eclipse over Australia to fine-tune their own corona-measuring techniques.

"We are learning how the wonderfully-detailed structures we see in the corona are shaped by the sun's magnetic field," astronomer and chair of the International Astronomical Union's Working Group on Eclipses Jay Pasachoff told NASA's news service. By studying how these structures change shapes regularly throughout the 11-year sunspot cycle, “we can use this information to improve predictions of the next solar cycle."

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