Astronomy: General

A Dictionary of Astronomy The Columbia Encyclopedia, 6th ed. Further reading

Ring Nebula

A Dictionary of Astronomy | 1997 | Copyright

Ring Nebula A 9th-magnitude planetary nebula about 2000 l.y. away in Lyra, also known as M57 or NGC 6720. The hot 15th-magnitude central star is surrounded by a shell of luminous gas and dust some three-quarters of a light year in diameter. In small telescopes the shell looks like an elliptical smoke ring 70″ × 150″ across. The ring is expanding at 19 km/s. Observations by the Hubble Space Telescope have demonstrated that the ‘ring’ is in fact a cylinder of gas aligned end-on to us.

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Ring nebula

The Columbia Encyclopedia, 6th ed. | 2011 | Copyright

Ring nebula planetary nebula in the northern constellation Lyra; cataloged as M57 or NGC 6720. It is perhaps the most famous and beautiful nebula of this type. Its name describes the appearance of the expanding shell of gas. The nebula is estimated to be more than 5,000 light-years distant.

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"Ring nebula." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. 1 Jun. 2012 <http://www.encyclopedia.com>.

"Ring nebula." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. (June 1, 2012). http://www.encyclopedia.com/doc/1E1-Ringnebu.html

"Ring nebula." The Columbia Encyclopedia, 6th ed.. 2011. Retrieved June 01, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1E1-Ringnebu.html

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