Image: Algol AB movie imaged with the CHARA interferometer

Description: Algol (β Persei) is a triple-star system (Algol A, B, and C) in the constellation Perseus, in which the large and bright primary Algol A is regularly eclipsed by the dimmer Algol B every 2.87 days. The eclipsing binary pair is separated by only 0.062 astronomical units (AU) from each other, so close in fact that Algol A is slowly consuming the less massive Algol B by continually stripping off Algol B's outer layers. This animation was assembled from 55 images of the CHARA interferometer in the near-infrared H-band, sorted according to orbital phase. Because some phases are poorly covered, B jumps at some points along its path. The images vary in quality, but the best have a resolution of 0.5 milliarcseconds, or approximately 200 times better than the Hubble Space Telescope. (A milliarcsecond is about the size of a quarter atop the Eiffel Tower as seen from New York City.) Tidal distortions of Algol B giving it an elongated appearance are readily apparent. Tidal distortions also result in "gravity darkening" effects, whereby in a significant number of images of Algol B, the edge or "limb" of the image is actually brighter than the center. (Baron et al., 2012)
Title: Algol AB movie imaged with the CHARA interferometer
Credit: http://www.oculum.de/newsletter/astro/100/60/2/2-02_algol_movie.gif, http://www.oculum.de/newsletter/astro/100/60/2/162.fa1cn.asp
Author: Dr Fabien Baron, Dept. of Astronomy, University of Michigan, Ann Arbor, MI 48109-1090
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