planetary nebula; NGC 6720, M 57
A large cloud of dust and gas released from and surrounding a massive hot star - typically associated with a Wolf-Rayet, O or very occasionally, a hot B star.
A ring nebula is a huge cloud of dust and gas that is shaped like a ring. Pictured above is M-57, a ring nebula in Lyra which is 2,000 light-years from Earth and was generated by a dying star (this nebula was discovered by Ch. Messier).
The Ring Nebula (also known as the Messier 57 or NGC 6720) is located in the constellation Lyra. It is among the most well known and recognizable examples of a planetary nebula. The nebula is located at 0.7 kpc (2300 light-years) from Earth and was discovered by Antoine Darquier de Pellepoix in 1779.
The Ring Nebula in Barnard's Galaxy has the official designation of Hubble 1925 III as it was the third (Roman numeral 3) object recorded in Hubble's 1925 paper, N.G.C. 6822, A Remote Stellar System. It includes areas of bright H II emission. In Paul W.