December 21, 1995
The Earth has carried you around the Sun again, steady as ever, while the stars kept their patient watch.
Hot Stars in the Trifid Nebula
Birthday · December 21, 1995
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APOD published December 21, 1995. Credit: Anglo-Australian Telescope Board. A publication-date match, not a photo taken on your date. Independent of NASA.
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.
Image credit: Anglo-Australian Telescope Board