Astronomy Picture of the Day

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

2023 April 2
A colorful oval nebula is shown star field is shown 
in a sparse starfield. Fainter red nebulosity surrounds the
bright oval. A relatively bright star is seen in the oval's
center.
Please see the explanation for more detailed information.

M57: The Ring Nebula from Hubble
Image Credit: NASA, ESA, Hubble Legacy Archive; Processing: Judy Schmidt

Explanation: It was noticed hundreds of years ago by stargazers who could not understand its unusual shape. It looked like a ring on the sky. Except for the rings of Saturn, the Ring Nebula (M57) may be the most famous celestial circle. We now know what it is, and that its iconic shape is due to our lucky perspective. The recent mapping of the expanding nebula's 3-D structure, based in part on this clear Hubble image,indicates that the nebula is a relatively dense, donut-like ring wrapped around the middle of an (American) football-shaped cloud of glowing gas. Our view from planet Earth looks down the long axis of the football, face-on to the ring. Of course, in this well-studied example of a planetary nebula, the glowing material does not come from planets. Instead, the gaseous shroud represents outer layers expelled from the dying, once sun-like star, now a tiny pinprick of light seen at the nebula's center. Intense ultraviolet light from the hot central star ionizes atoms in the gas. The Ring Nebula is about one light-year across and 2,500 light-years away.

Tomorrow's picture: the beasts at the center of our galaxy


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