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.

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.

Ring Nebula

[′riŋ ′neb·yə·lə]
A nebula in the summer constellation Lyra; it is an example of the planetary type of gaseous nebulae.
References in periodicals archive ?
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.
Heritage astronomer Howard Bond said: "We chose the Ring Nebula as our first new target, in part, because it is well known among amateur astronomers.
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.
We all knew that the ring nebula was near the zenith, and decided to search for it after we got some dark-background readings.
If we could see the Ring Nebula from the plane of its equator, it might look much like our next object, the Dumbbell Nebula (M27) in Vulpecula, the Little Fox.
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.
This outstanding ring nebula appears quite round in shape, with a sharply defined edge, slowly dimming towards the centre.
Summer constellations will still be high in the sky, allowing society members to train their telescopes on such wonders as the great star cluster in Hercules, the beautiful double star Alberio and the Ring Nebula.
THE RING NEBULA, Messier 57 in Lyra now rising up the eastern evening sky, is a familiar target for astronomers of every stripe.