Although it looks like a ring, the Helix Nebula is actually a trillion kilometre-long tube of glowing gas seen from one end. The gas was thrown out from a dying Sun-like star in the process of changing from a red giant into a white dwarf, creating what is known as a planetary nebula. This image combines a wide view made by the KPNO 0.9 metre telescope in Arizona with the sharpness of an image from the Hubble Space Telescope.
Credit: Image made in visible light by M. Meixner and T. Rector for NOAO and the NASA / ESA Hubble Heritage Team.
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