Close encounter with sun-like star
Researchers at the University of St Andrews are part of an international team which has captured the first close-up image of the surface of a sun-like star beyond the solar system.
The image of Altair, one of the brightest stars in the night sky, was captured by combining the might of four telescopes, which together simulate a giant instrument the size of three football pitches.
St Andrews’ physicist Dr Ettore Pedretti was a member of the team – led by the University of Michigan – which combined the light of four telescopes 300 meters apart in California to capture the powerful image of the rapidly rotating hot star.
Dr Pedretti said, “The most powerful stars in the galaxy share much more in common with Altair than the Sun, and we are just now learning if our theories of these objects are correct.
“Like the lidless staring eye of Sauron in the Lord of the Rings, our instrument can peer over great distances to reveal the secrets of the stars.”
The resulting image, roughly 100 times sharper than those provided by the Hubble Space Telescope, provides new insights into the star. Researchers are able to confirm that Altair is a rapidly spinning non-spherical body and describe the moving image as `like a twirling ball of pizza dough.’
Twice the size of the sun, Altair is the brightest star in the constellation Aquila, the Eagle and is 16.7 light years from the Earth. Though it can be clearly seen by the naked eye in the Northern Hemisphere, it has not been possible until now to develop a telescope powerful enough to provide a close-up view.
The innovative light-combining technique used to view the star is called optical interferometry. Dr Pedretti was responsible for building the infrared camera used to take superfast ‘snapshots’ of the combined light of four telescopes ‘it has to be very fast in order to ‘freeze’ it against the turbulent atmosphere.
Dr Pedretti now aims to form the first group in Scotland which will build instruments for optical and infrared interferometry.
“My aim is to exploit existing interferometers around the world in order to take detailed pictures of distant and interesting astronomical objects that are not achievable even with the largest single telescopes,” he said.
The research appears in this week’s issue of Science. Dr Pedretti is a SUPA (Scottish Universities Physics Alliance) postdoctoral fellow at the University of St Andrews.
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Ref: Close encounters 040607
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