A planetary nebula, often abbreviated as PN or plural PNe, is a kind of emission nebula consisting of an expanding glowing shell of ionized gas ejected from old red giant stars late in their lives. The word `nebula` is Latin for mist or cloud and the term `planetary nebula` is a misnomer that originated in the 1780s with astronomer William Her...
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http://en.wikipedia.org/wiki/Planetary_nebula
any of a class of bright nebulae that are expanding shells of luminous gas expelled by dying stars. Observed telescopically, they have a relatively ... [6 related articles]
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http://www.britannica.com/eb/a-z/p/76
The Ring Nebula (M57) in Lyra. Hubble Telescope image A luminous shell of gas, often of complex structure, cast off and caused to fluoresce by an evolved star of less than about 4 solar masses. Planetary nebulae have nothing to do with planets other than their name, which was coined by William...
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http://www.daviddarling.info/encyclopedia/P/planneb.html
A shell of gas ejected from, and expanding about, a certain kind of extremely hot star.
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http://www.encyclo.co.uk/local/20040
A shell of gas that surrounds a small, dense, hot star. The name is misleading because planetary nebulae have no connection with planets. They probably got their name because some of these nebulae appear disk-like and may have been initially mistaken for planets.
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http://www.encyclo.co.uk/local/20448
A shell of gas surrounding a small, white star. The gas is usually illuminated by the star, producing a variety of colors and shapes.
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http://www.seasky.org/astronomy/astronomy-glossary.html
A very hot star surrounded by expanding gases that give off a glow because of intense radiation from the star.
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http://www.solarspace.co.uk/Glossary3.php
[
n] - a nebula that was once thought to be a star with its planets but is now thought to be a very hot star surrounded by an expanding envelope of ionized gases that emit a fluorescent glow because of intense radiation from the star
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http://www.webdictionary.co.uk/definition.php?query=planetary%20nebula
A bright cloud of dust and gas surrounding an old star, namely a red giant. Towards the end of its life the star ejects the dust and gas violently, losing most of its mass and becoming a white dwarf. The nebula disappears after approximately 100 000 years. They are called 'planetary' because originally astronomers thought they looked like planetary...
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https://www.encyclo.co.uk/local/20687
noun a nebula that was once thought to be a star with its planets but is now thought to be a very hot star surrounded by an expanding envelope of ionized gases that emit a fluorescent glow because of intense radiation from the star
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https://www.encyclo.co.uk/local/20974
Shell of gas thrown off by a star at the end of its life. Planetary nebulae have nothing to do with planets. They were named by German-born English astronomer William Herschel, who thought their rounded shape resembled the disc of a planet. After a star such as the Sun has expanded to become a red giant, its outer layers are ejected into space ...
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https://www.encyclo.co.uk/local/21221
A nebula of gas surrounding a star.
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https://www.encyclo.co.uk/local/22784
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