"At the heart of this cloud glows a dead red giant, the immediate afterlife of a medium-mass star like our Sun. After core fusion shut down, the star began shedding gas, forming a planetary nebula. “Planetary” is a misnomer—the nebula is all about that dead red star."
Spanning 2.5 light years, the Helix gas cloud has a puzzling shape: two rings instead of one. An inner disk is bisected by an outer one tilted at almost 90 degrees. As the nebula orbits the Milky Way, the leading edge collides with interstellar matter and flattens.
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Cometary Knots
Thousands of knots of gas swarm the edge of the inner disk, trailing comet-like tails. Each knot is twice as big as our solar system. They form when fresh, hot gas overruns cooler gas and condenses. The tails stretch away from the star, blown by relentless stellar wind.
Double Ring
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Ring Nebula
A typical planetary nebula persists for only 10,000 years or so before the gas dissipates. The Ring Nebula is a young one that’s still growing. Ultraviolet light from its fading star energizes the gas, making it glow.
Helix Nebula Rank 3
Tycho’s Supernova
On November 11, 1572, astronomer Tycho Brahe saw a type 1a supernova. As a dead red giant shed its shell, a white dwarf lapped up the gas. When the dwarf hit critical mass, a nuclear chain reaction triggered an explosion. The remnant, a planetary nebula, still glows.
Helix Nebula Rank 6
Trivia[]
Real image of Helix Nebula from the Hubble Space Telescope
Helix Nebula (also known as NGC 7293 or Caldwell 63) is a planetary nebula located in the constellation Aquarius.