Dark Nebulae / Emission Nebulae / Planetary Nebulae / Reflection Nebulae / Supernova Remnants
Ring Nebula
Right Ascension 18 : 53.6 (h:m)Declination +33 : 02 (deg:m)
Distance 2.3 (kly)
Visual Brightness 8.8 (mag)
Apparent Dimension 1.4x1.0 (arc min)
Discovered by Antoine Darquier de Pellepoix in 1779.
The famous ring nebula M57 is often regarded as the prototype of a planetary nebula, and a showpiece in the northern hemisphere summer sky. Recent research has confirmed that it is, most probably, actually a ring (torus) of bright light-emitting material surrounding its central star, and not a spherical (or ellipsoidal) shell, thus coinciding with an early assumption by John Herschel. Viewed from this equatorial plane, it would thus more resemble the Dumbbell Nebula M27 or the Little Dumbbell Nebula M76 than its appearance we know from here: We happen to view it from near one pole.
This is contrary to the belief expressed e.g. in Kenneth Glyn Jones' book. There are even indications from investigations of deep observations such as George Jacoby's deep photos obtained at Kitt Peak National Observatory that the overall shape might be more that of a cylinder viewed along the direction of the axis than that of a ring, i.e., we are looking down a tunnel of gas ejected by a star at the end of its nuclear-burning life. Eventually, these observations have given evidence that the equatorial ring or cylinder has lobe-shaped extensions in polar directions, similar to those found in deep images of M76, but even more resembling other planetaries like NGC 6302, see e.g. the review by Sun Kwok (2000).
