Alcor A and Alcor B

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Dscovery image of Alcor B, marked with the green arrow in the inset. Alcor B is a red dwarf star that orbits the star Alcor. Alcor is located some 25 parsecs away and can be seen in the middle of the Big Dipper's handle.

Project 1640 astronomers discovered the faint star with the 200-inch Hale Telescope by blocking out almost all of Alcor's light with a coronagraphic mask, the darker circular region in the middle of the image. Although the vast majority of Alcor's light has been blocked out, a residual halo of speckles remains because of minute imperfections in the cameraƕs optics. The actual diameter of either of the stars far smaller than a pixel in this image. This residual glare is what makes finding faint companions of bright stars difficult. Credit: Project 1640, American Museum of Natural History, Digital Universe Atlas.

Press Release on Discovery of Alcor B

See also: A Companion for Alcor

The research was based on observations obtained at the Hale Telescope, Palomar Observatory, as part of a collaborative agreement between the California Institute of Technology, its divisions Caltech Optical Observatories and the Jet Propulsion Laboratory (operated for NASA), and Cornell University.

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