Ring nebula

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Related to Ring nebula: planetary nebula

Ring nebula,

planetary nebulanebula
[Lat.,=mist], in astronomy, observed manifestation of a collection of highly rarefied gas and dust in interstellar space. Prior to the 1960s this term was also applied to bodies later discovered to be galaxies, e.g.
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 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

A ring or arc of nebulosity centered on and ionized by ultraviolet radiation from a Wolf-Rayet star. The Ring nebula is, confusingly, not a ring nebula.

Ring nebula

(M57; NGC 6720) A ring-shaped planetary nebula, about 1′ across, in the constellation Lyra. The inner regions closest to the centrally placed ionizing star are green as a result of light emitted by doubly ionized oxygen; there is an approximately symmetrical transition to the reddish outer edge where the lower-energy transitions of hydrogen and nitrogen are responsible for the color. See emission nebula.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006

Ring Nebula

[′riŋ ′neb·yə·lə]
A nebula in the summer constellation Lyra; it is an example of the planetary type of gaseous nebulae.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
NGC 6572's surface brightness is 100 times greater than the Ring Nebula's, so it will handle magnification well, but I've found that it looks brightest and greenest with just enough magnification to make it bigger than a point source.
The Ring Nebula is about 2,000 light-years from Earth and measures roughly 1 light-year across.
At the base of the telescope, people stand on the second step of a small ladder to reach the eyepiece while one of the volunteer guides tells one youngster about the object he's seeing, the Ring Nebula.
First catalogued more than 200 years ago by the French astronomer Charles Messier, the Ring Nebula is composed of material cast off by a dying star.
In one case, for instance, the ring nebula surrounding the star is about 20 light-years across while the large dust shell is 160 light-years across.
Mayfield explains what happened: "Their original objective was to sight in onsome of the fainter stars, but, to their surprise and excitement, they inadvertently focused on a ring nebula and received outstanding resolution."
M57, the Ring Nebula in Lyra, and M27, the Dumbbell Nebula in Vulpecula, lie on a line with the renowned double star Albireo, or Beta ([beta]) Cygni, which shines about midway between them.
But a lot more magnification reveals it as a dimly glowing doughnut: M57, the Ring Nebula. It's extremely tiny Compared to the green ring on the map.
This outstanding ring nebula appears quite round in shape, with a sharply defined edge, slowly dimming towards the centre.
To many people summer planetaries mean the Ring Nebula or the Dumbbell, but there are numerous other objects which deserve investigation, and one of them is NGC 7008 in Cygnus.