Astronomy Picture of the Day

Discover the cosmos! Each day we feature a different image or photograph of our fascinating universe, along with a brief explanation written by a professional astronomer.

December 21, 1995
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Hot Stars in the Trifid Nebula
Credit: Anglo-Australian Telescope photograph by David Malin
Copyright: Anglo-Australian Telescope Board

Explanation: In the center of the glowing red gas on the Trifid Nebula lies an open cluster of young hot stars. The energetic light from these stars strikes hydrogen atoms in the surrounding nebula causing them to lose their electrons. When an electron finds its way back to a hydrogen proton, it emits light at very specific colors - one of which is the red color of the nebula seen here. The red glow is thus indicative of an emission nebula. The dramatic dark sheets are made of interstellar dust grains, tiny needle shaped pellets which are thought to be created and expelled in the atmospheres of cooler stars.

Tomorrow's picture: Summer at the South Pole

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