Citizen Scientists Help Astronomers Solve Space Mystery

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A University of Alberta physicist brought together backyard astronomers and professionals to confirm the mysterious behavior of two stars more than 300 light-years from Earth.

U of A astrophysics researcher Gregory Sivakoff was part of an international team that re-examined an established theory about periodic bursts of light coming from a binary star.

The two stars are called a binary star because they rotate around each other. The accepted theory on why the binary star, named SS Cygni, emits periodic bursts of light involves an interaction between the pair.

Sivakoff explains that one of the stars, a normal star that is a lower-mass cousin to our Sun, loses bits of its outer envelope to its neighbor, a white dwarf, which is as massive as our Sun but squeezed down to the size of Earth.

"Gravity continuously draws material from the normal star's envelope, but it is only when the material rushes towards the white dwarf that we get an outburst of light," said Sivakoff. "We see these outbursts happen about every 35 to 65 days."

The periodic light flash theory of SS Cygni was developed in the early 80s. Sivakoff says a key factor in the theory's calculations is the distance between Earth and SS Cygni.

In 1999 researchers with NASA's Hubble telescope came up with a larger distance from Earth to the binary star. Sivakoff says that put the established theory into question.

To settle the distance issue Sivakoff and researchers from Australia, Britain, the Netherlands and the U.S. set out to re-measure the distance between Earth and the binary star.

Over the course of two years Sivakoff worked with a worldwide network of 180 amateur astronomers who used their optical telescopes to watch the night skies and report whenever SS Cygni began one of its outbursts.

The researchers then called on ground-based networks of radio telescopes to make the distance calculation. By the end of 2012, the researchers confirmed that a smaller distance of about 370 light-years from Earth to the binary star was correct.

"That was what we need to reconfirm the theory for periodic bursts of light from SS Cygni," said Sivakoff.

Sivakoff describes the research as a big win for citizen scientists.

"We would not have been able to vindicate the theory if dedicated amateur astronomers using their own equipment hadn't volunteered to help us," said Sivakoff.

Sivakoff is the second author of the research, which is published in the May 24 issue of the journal Science [http://www.sciencemag.org/content/340/6135/950].

Contact:
Brian Murphy
University of Alberta
Marketing and Communications
+1 780-235-6267
brian.murphy@ualberta.ca

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