Ring Nebula (M57, NGC 6720)
One of the best known planetary nebulae and the second to be discovered, by the French astronomer Antoine Darquier
(1718-1802) in 1779 (15 years after the first one, the Dumbbell
Nebula). It is located in the constellation Lyra.
The central star, which has a visual magnitude of 14.7 and a surface temperature
of over 100,000 K, was discovered by the German astronomer F. von Hahn in
Although appearing as a flattened ring, M75 is actually toroidal or possibly
even cylindrical in shape; we simply happen to be looking more or less down
one of its poles. Viewed along its equatorial plane, the Ring would more
closely resemble a filled-in planetary, such as the Dumbbell. Sensitive
observations have also shown that the toroid or cylinder has lobe-shaped
extensions in polar directions, and also a halo of material extending to
over 3.5' (2.4 light-years) – remnants of the central star's earlier stellar winds before the nebula itself
M57 is easy to find, between Beta and Gamma Lyrae, at about one-third the
distance from Beta to Gamma. It can be seen with binoculars as an almost
stellar object. In small amateur telescopes, the ring becomes apparent at
about 100 magnification. If ever color is notable, the Ring appears greenish
because most of its light is emitted in few green spectral lines. Even in
small scopes, a slight ellipticity is noticeable, with a major axis at a
position angle of about 60°. Under good seeing conditions, large instruments
may reveal the central star, together with several very faint stars that
lie in the foreground or background of the nebula's extension.
|© Torsten Bronger
||1.4' × 1'
||~2,300 light-years (700 pc)
||R.A. 18h 53m 35.1s,
Dec. +33° 01' 45.0"
||HD 175353, PN G063.1+13.9,
BD+32 3246, GCRV 11366,
PK 063+13 1
|M57, the Ring Nebula, imaged by the
Hubble Space Telescope
AND STAR CLUSTERS