The reconstructed image shows the development of the beginning of the eclipse of the main star in the binary star system Epsilon Aurigae. The images were taken from the Center for High Angular Resolution interferometer using the newly developed Michigan Infrared Combiners. Credit: John D. Monnier, University of Michigan
Reading a century-old puzzle of astronomy is solved: US researchers have tracked down the cause of the star eclipse in the binary star system Epsilon Aurigae. High-resolution photos show for the first time the identity of the object, which temporarily obscures the visible star: a huge flat dust disk. A newly developed instrument, the so-called Michigan Infrared Combiner, allowed the researchers to assemble and amplify the images captured by four different telescopes. Eclipses of the sun or other stars are spectacular phenomena and have often led to important astronomical findings in the past. Although many stars are eclipsed, most of them can not be observed from Earth. Unlike the so-called double star Epsilon Aurigae: As recorded from the year 1820, astronomers were able to observe an eclipse of the bright main star almost 200 years ago. They assumed that it was a companion responsible, but this could not be identified. The 18-month eclipse only occurs every 27.1 years and reduces the brightness of the star by 50 percent. However, the mystery was the eclipse for another 190 years, for the dark object that moved in front of the star could not be described in any detail, despite its size, to which the long duration of the darkness pointed.

Until it was time again in 2009: The star darkened again after about 27 years. But this time the researchers were prepared: They developed a new instrument that uses the so-called interferometry, to superimpose images of the starry sky of different telescopes. Through this interconnection of the telescopes, they received a high-resolution image of the main star and the obscuring object. Earlier conjectures proved to be correct: the object is actually the smaller companion of the main star? However, the huge dark dust disk that covers it is responsible for the darkening. This swallows the light so well that the little star is difficult to observe. While circumnavigating his big brother, he partially covers it with his huge coat of dust.

"So far, no other star system is known that works that way, " co-author John Monnier points out. In addition, for the first time during a star eclipse high-resolution images of the stars involved could be made. Among other things, astronomers can calculate the dimensions of the three objects involved in the eclipse. So is the diameter of the dust disk around 570 million kilometers? that is about four times the distance Earth-Sun.

Brian Kloppenborg (University of Denver) et al .: Nature, Vol. 464, No. 7290, p. 870, doi: 10.1038 / nature08968 ddp / Thomas Neuenschwander advertisement


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