THIS IMAGE OF the Ring Nebula or Messier 57 was obtained using the Wide Field Camera on the Isaac Newton Telescope in the Canary Islands.
The Ring Nebula is often regarded as the prototype of a “planetary nebula“. But despite the name, a planetary nebula has nothing to do with planets. The moniker was given because such objects did not look sharp and star-like when seen through early telescopes; rather, they appeared as distinct blobs or discs, and in that sense their appearance resembled that of planets.
A planetary nebula forms when an elderly star puffs off its outer gas layers. Afterwards, intense radiation from the exposed core of the star heats up the gas, making it glow. It is the final stage in the life of Sun-like stars, and results in the remnant stellar core becoming a white dwarf.
Many planetary nebulae are full shells of gas surrounding the star on all sides. But observations have shown that the Ring Nebula is, most probably, actually a ring (torus) surrounding its central star, and not a spherical (or ellipsoidal) shell.
This nebula is located approximately 2,300 light-years from Earth. Astronomers estimate that the gas cloud has been expanding away from the star for about 1,600 years (plus or minus about 240 years).
The image is a three-colour composite made from data collected using filters to isolate the light emitted by hydrogen alpha (H-alpha), doubly ionised oxygen (OIII) and ionised sulphur (SII) atoms, and coded in the image as red, green and blue respectively.
See the full-size, high-resolution image here (will open in a new window or tab).
Text adapted from Information issued by IAC. Image obtained and processed by members of the IAC astrophotography group (A. Oscoz, D. López, P. Rodríguez-Gil and L. Chinarro).
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