For more than a century, there has been a mystery. For decades there have been hypotheses. For years, University of Denver astronomy professor Robert Stencel has sought answers.
But never has there been an image. Until now.
Stencel and DU PhD student Brian Kloppenborg are co-authors of a paper appearing April 8 in the international science journal Nature. The paper details how they worked with teams from Georgia State University and the University of Michigan to capture an image of the mysterious binary star system Epsilon Aurigae (pronounced EP-sih-lon aw-RYE-jay).
The system, with one bright star that appears to “blink” every 27 years, was discovered in 1821. The blink, which is actually an eclipse, lasts for two years. The cause of the eclipse was unknown. Some astronomers suggested an orbiting twin star or a black hole, but there was no way to capture an image and be sure until now.
Stencel has studied the system since the 1980s and was joined by teams of scientists and even amateur astronomers — all funded by four separate National Science Foundation grants. Stencel and the teams from Michigan and Georgia tested Stencel’s proposal to combine the University of Michigan’s newly developed imager and software with Georgia State’s giant array of conjoined telescopes based in the California mountains near Los Angeles to produce a snapshot of what exactly is going on during the current eclipse.
The combined power of Georgia State’s array on Mt. Wilson in southern California couldn’t be reproduced by any single earth-bound telescope, Stencel says.
“What we’re seeing has been the subject of hypotheses for decades, what we’ve never had was a ‘picture’ of what is actually happening,” Stencel says. “What we’ve produced is a reconstruction of an image based on sampling done with multiple telescopes. A reasonable analogy is what you ‘see’ with MRI (magnetic resonance imaging). You don’t have a shutter going off, but you’ve scanned the object repeatedly, and after a while the computer has enough information to put together a picture.”
For the first time, scientists are seeing what’s happening some 2,000 light years away — a huge star 150 times the mass of our sun is being eclipsed by a whirling dust cloud some 930 million miles across.
“What we’re seeing, that we’ve never seen before, is this giant cloud,” Stencel says. “It’s just that, a giant, dense cloud of dust.”
Because astronomers had not been able to see much light from the system, theories had described it as a smaller star orbited by a disk of dust that had to be precisely aligned with the star’s orbit and then again aligned along the same plane as the earth’s orbit. It was all very unlikely, but the theory explained observations.
These new images show that as nearly impossible as that seems, it is the case.
“This really shows that the basic paradigm was right, despite the slim probability,” says University of Michigan professor John Monnier. “It kind of blows my mind that we could capture this.”
Stencel says getting everything to work — from the funding to a “Citizen Sky” initiative that encouraged amateur astronomers to help assemble data to getting the critical telescope time from the California array — took an immense amount of time and work, and a bit of luck. This plus the work of graduate students such as Kloppenborg, who process the volumes of raw data, make the discoveries possible.
In fact, with the valuable telescope viewing time arranged as the once-in-27-year eclipse happened, everything almost came apart in 2009 when fires raged through the California mountains and threatened the observatory. The authors in their story thank the firefighters who saved the telescopic array, a collection of lenses that span some 300 yards. Then, shortly after the fires, a bad rainy season caused mudslides that damaged the access road to the site, nearly jeopardizing the scientists’ plans to conduct more observations. The astronomers remain hopeful that they will witness the end of the last half of the eclipse. It will be their last chance to see the event until 2037.
“We have witnessed the initial phases of this eclipse,” Kloppenborg says. “We certainly don’t want to miss the rest of the show.”
“This has been a very good project for all of us,” Stencel says. “We have a picture of something that until now we’ve only had hypotheses. We are certainly not done, but this is a big step forward.”
Stencel says the work would not have been possible without the bequest of William Herschel Womble in support of astronomy at the University of Denver.
The journal Nature, published since 1869 and widely read by the scientific community worldwide, is online at www.nature.com.