Big Dipper's Alcor A and B (IMAGE)

American Museum of Natural History

Big Dipper's Alcor A and B

Caption

Alcor, a star in the middle of the Big Dipper's handle, has a newly found red dwarf companion (circled in green). Project 1640 astronomers discovered the faint star by blocking out almost all of Alcor's light with a coronagraph. The halo of speckles around the coronagraph's occulting mask is caused by the wave-like properties of light from Alcor's residual glare. The actual diameters of both stars take up just a tiny fraction of a pixel.

Credit

Project 1640/AMNH and Digital Universe Atlas

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