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M57 : The Ring Nebula   IC 418: The Spirograph Nebula  
  M57 : The Ring Nebula     IC 418: The Spirograph Nebula

Hubble Space Telescope has captured the sharpest view yet of the most famous of all planetary nebulae: the Ring Nebula (M57), first cataloged more than 200 years ago by French astronomer Charles Messier. The pictures reveal that the "Ring" is actually a cylinder of gas and dust  around a dying star. Elongated dark clumps of material are embedded in the gas at the edge of the nebula; the dying central star floating in a blue haze of hot gas. Blue emission is from very hot helium, which is located primarily close to the hot central star. Green represents ionized oxygen, which is located farther from the star. Red shows ionized nitrogen, which is radiated from the coolest gas, located farthest from the star. The gradations of color illustrate how the gas glows because it is bathed in ultraviolet radiation from the remnant central star.


Glowing like a multi-faceted jewel, the planetary nebula IC 418 represents the final stage in the evolution of a star similar to our Sun. The star at the center of IC 418 was a red giant, but then ejected its outer layers into space to form the nebula. The stellar remnant at the center is the hot core of the red giant, from which ultraviolet radiation floods out into the surrounding gas, causing it to fluoresce. Red shows emission from ionized nitrogen (the coolest gas in the nebula, located furthest from the hot nucleus), green shows emission from hydrogen, and blue traces the emission from ionized oxygen (the hottest gas, closest to the central star). The remarkable textures seen in the nebula are newly revealed by the Hubble telescope, and their origin is still uncertain. Our own Sun is expected to undergo a similar fate, but this will not occur until some 5 billion years from now.

Krešimir J. Adamić