M57 (NGC 6720), Ring Nebula
Mag. - 8.8
Constellation - Lyra
Distance - 2,300 light years [estimated],
Size - 0.9 light years [estimated]
Messier 57 was the second planetary
nebula to be discovered [Messier 27 was the first]. Messier 57
was first described by Antoine Darquier de Pellepoix in January 1779, and was
also independently "discovered" by Charles Messier on January 31,
1770 and entered into his catalogue. The object we see is the
result of the ejection of approximately 0.2 solar mass of material from the
faint star seen in the middle of this object. It is estimated that the
width of the Ring Nebula is 0.9 light years. Although a source of debate
for years, it is now generally accepted by astronomers that the apparent shape
of the Ring Nebula from our perspective is due to the fact that our line of
sight is down one of the poles of a cylinder or tube-shaped object.
Messier 57 is an easy object in most amateur telescopes. In larger
telescopes a green color is readily apparent due to the fact that most of the
nebula's emissions fall within the green area of the spectrum.
