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+ - Rare Eclipsing Binaries Provide a New Tape Measure for the Universe

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Hugh Pickens writes
Hugh Pickens writes writes "Kate Taylor repotrs that astronomers have figured out a way to make much more accurate measurements of the distance to our neighboring galaxy, the Large Magellanic Cloud (LMC), using rare class of double star known as eclipsing binaries. By tracking changes in the binary's brightness very carefully, and also measuring the stars' orbital speeds, it is possible to work out how big the stars are, their masses and other information about their orbits. When this is combined with careful measurements of the total brightness and colors of the stars, remarkably accurate distances can be found. "I am very excited because astronomers have been trying for a hundred years to accurately measure the distance to the Large Magellanic Cloud, and it has proved to be extremely difficult," says Wolfgang Gieren of the Universidad de Concepción, Chile. "Now we have solved this problem by demonstrably having a result accurate to two percent." Improving the accuracy of the measurement has the side effect of improving knowledge of the Hubble Constant, the rate of expansion of the universe, and therefore of of the mysterious dark energy that is causing the expansion to accelerate. "We are working to improve our method still further and hope to have a one percent LMC distance in a very few years from now," says Dariusz Graczyk of Warsaw University Observatory. "This has far-reaching consequences not only for cosmology, but for many fields of astrophysics.""
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Rare Eclipsing Binaries Provide a New Tape Measure for the Universe

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Never underestimate the bandwidth of a station wagon full of tapes. -- Dr. Warren Jackson, Director, UTCS