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Unstrange Phenomena

21 January 2011

What Is The 200 Year Mystery of Epsilon Aurigae?

Check out the latest findings to answer the 200 year old questions baffling astronomers.

Artist rendition of Epsilon Aurigae

From Denny: For a couple of centuries now astronomers have been baffled by the star Epsilon Aurigae (pronounced EP-si-lon au-RYE-gee). They have been frustrated to discover the reason why the brightness of the star always dims for about a two year period. The star's light fluctuates regularly in a cycle of about 27.1 years.

In the winter sky this time of year look up to see Polaris and to the northeast The Big Dipper. Now track along to Capella and just to the right of that is Epsilon Aurigae and it's quite faint. We are in that dim cycle for the star from 2009 to 2011.

Brian Kloppenborg and 16 other astronomers solving the mystery

Brian Kloppenborg, an astronomer at Mt. Wilson located more than a mile above Los Angeles, California, has been studying this distant neighbor star - with great success - since 2008. In the astronomy community he has acquired a bit of a rep for trying to unravel the two century mystery concerning the light fluctuations of this distant star.

Kloppenborg has published in the science journal "Nature" and excited both amateur and professional astronomers to aid him in his quest. This distant star has acquired a celebrity status in astronomy circles, even its artwork and its own song where it lives on a lyric in a rock ballad called "We Are The Stars" for inspiration. After all, night after night, out in the winter cold, dutiful astronomers need something to keep them going. A little cult status is helpful. :)

Just how distant is Epsilon Aurigae? It hangs out in the massing swirls of our beautiful Milky Way and is 2,000 light years away from Earth.

When the astronomy mystery first began

How did this fascination with the star's light begin? About two centuries ago a German government minister, Johann Fritsch, looked up into his winter night sky and wondered why what was normally the fifth brightest star in the constellation Auriga had suddenly dimmed.

Fritsch was so intrigued that he wrote a letter to a publisher of star almanacs asking if anyone else had witnessed the same in the night sky. That question of his soon became a real challenge to the astronomers of his day. Why did Epsilon Aurigae lose half its brightness for almost two years in a 27 year cycle? Given the star's mass, for over 175 years, astronomers have known it is dimmer than it should be.

Various ideas were tossed out for consideration by the astronomers of the day to explain what caused the eclipse of Epsilon Aurigae:

A swarm of meteorites.

A black hole.

A large and dusty cloud.

Or a disk like the rings of Saturn.

New technology of The CHARA Array

Well, today, we have more technology to help us unravel the mysteries of the skies. One such tech lovelie is The CHARA Array. It is an optical interferometer. An interferometer is a group of six, widely spaced telescopes, accompanied by a labyrinth of trolleys, mirrors and vacuum-sealed conduits. The CHARA Array amplifies the light so that it seems to be coming through a device 100 times larger than the Hubble Space Telescope.

All these tech goodies combine in a symphony to bring starlight into a stunningly precise resolution. Let's put it this way: If Big Business decided to build a shopping mall on planet Mars, well, our tech girl CHARA could count every parking space accurately. Impressive.

Focusing this array on a star 2,000 light years away will help us to accurately define the specific properties of the star system. This is the first time astronomers can see the shape and surface characteristics of stars. Up until now, even with the largest telescopes, stars were mere points of light.

"We are in a period when it is becoming possible to see star systems in detail," says science writer Timothy Ferris. "One reason these studies are important is because they shed light on how our star and our planet got here — and the story of how the Earth got here is also the story of how human beings came to be here."

Epsilon Aurigae Nature article, a turning point in understanding the star

Kloppenborg, 27-year-old graduate student at the University of Denver, was the lead author but he had a team of 16 fellow astronomers that collaborated to do the long hours of work.  "Infrared Images of the Transiting Disk in the Ε Aurigae System" was based upon two observations from Mt. Wilson in the fall of 2009.  Kloppenborg and colleagues explained the eclipse.  They provided images and specifications of the objects in the star system.

What did they discover new about Epsilon Aurigae? 

They discovered the diameter of the star is nearly 270 times our Sun's.  Another object that had baffled astronomers for centuries is the thin, dark cloud shaped like a pancake when viewed from the side.  It turns out that pancake cloud consists of carbon and silicon that is caught in a haze of hydrogen and helium gases.  Check it out, the diameter of that dark pancake cloud is practically 1,300 times the Sun's.  Hubble Space Telescope has detected ultraviolet emissions coming from within the cloud.  That indicates the presence of a second star!

Reactions to the Epsilon Aurigae discovery

Astronomers can be a romantic and melodramatic lot.  Check out their comments:

From an astronomer at the University of St. Andrews in Scotland, who also assisted with the research, cited the Old Testament and Tolkien in one sweeping statement.

"Like David, tiny particles of dust are able to kill the light of this 'Goliath' star. It is 'like seeing the vessel of the sun … being swallowed by the dragon Smaug.'"

Kloppenborg thinks "the eclipse looks a little like Pacman, whose body is the star and whose ghost-eating maw is this large, dusty object slowly cutting across it."

Kloppenborg's time is running out to study the Epsilon Aurigae eclipse. It began in 2009 and ends this Spring of 2011. By the time Kloppenborg finishes his dissertation in 2012 he hopes to have nailed down the age of the star. He believes this star is at the end of its life, shedding its outer layer as it dies ever so slowly. This explains the castoff material that has been captured and shaped into the pancake cloud by the gravity of a hidden second star detected by Hubble.

Kloppenborg's theory is a radical departure from the current astronomical thought that was derived from previous eclipses. Conventional thought believes that this visible star is actually younger and burning more steadily. They think the pancake cloud is actually debris left over from the creation of the entire star system which is now caught in the gravitational pull of that second hidden star. Those astronomers hold the belief that a planetary system could develop out of this debris.

Only time - and many observations - will tell the full story of this distant star in our celestial neighborhood. The next viewing of Epsilon Aurigae? Try 2036. Make a date and be there.

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