Picture of the Week: The Witch Head Nebula

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The Witch Head Nebula—formally named IC 2118—sits in the constellation Orion about 1,000 light years from Earth. (In case you're having a hard time seeing the witch, her face is in profile facing to the right.) That bright blue star in the center of the image is Rigel, Orion's brightest star and the sixth-brightest in our sky. The star is responsible for the nebula's blue glow, but it doesn't appear that color because Rigel is a blue star. Rather, the dust grains simply reflect blue light more efficiently than red wavelengths. It's much the same reason that our own sky is blue.

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