nebulaic fireworks

new pic of the helix nebula.

"...Unlike real fireworks, the scene in the Helix Nebula involves no explosion. Rather, as a sun-like star ages, it ejects material in stages over tens of millions of years. A wind of charged particles continues to flow from the aged star, and the wind runs into the previously ejected layers, creating shock waves. Radiation from the star ionizes atoms in these outward-racing crash sites. Tiny particles are forced together and emit light. The knots might be remnants of planets that once existed around the star, astronomers figure. Or perhaps they involve material ejected from the star at some stage in its life. Nobody knows..."

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