The Ring Nebula is often considered the leader of a class of celestial objects known as “planetary nebulae”. The image above was produced by astronomers from the Isaac Newton Group of Telescopes in the Canary Islands.
Despite the term, planetary nebulae have nothing to do with planets. They got their name from observations using early telescopes, through which they looked like small blobs instead of pinprick stars. In this respect, they resembled the discs or faces of planets, and the name has stuck ever since.
In reality, a planetary nebula is a huge cloud of gas that has been “puffed” off by a star in the final stages of its life. Our Sun will eventually go through this phase.
The Ring Nebula, also known as M57 (being the 57th entry in the catalogue compiled by the 18th-19th century French astronomer Charles Messier) is 2,300 light-years from Earth. At its centre is a white dwarf star…the “burned out” remains of a normal type of star.
Some planetary nebula are spherical-shaped clouds that completely surround their central star. The Ring Nebula, though, is thought instead to be a ring (or torus, like a donut) surrounding the white dwarf and fortuitously seen face-on by Earth-bound astronomers.
The image above is a false-colour composite that shows emission from certain specific types of gas in the nebula: hydrogen (shown as red), doubly ionised oxygen (green) and ionised sulphur (blue).
See the full-size, high-resolution version here (new window).
The photos below give two other views. First, a Hubble Space Telescope image that shows the nebula in approximately true colour; and second, an infrared view from the Spitzer Space Telescope.
Top image courtesy of the Isaac Newton Group of Telescopes; image obtained and processed by members of the IAC astrophotography group (A. Oscoz, D. López, P. Rodríguez-Gil and L. Chinarro).
Middle image courtesy The Hubble Heritage Team (AURA / STScI / NASA).
Bottom image courtesy NASA / JPL-Caltech / J. Hora (Harvard-Smithsonian CfA).
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