RING NEBULA

The Ring Nebula (also catalogued as Messier 57, M57 or NGC 6720) is a planetary nebula in the mildly northern constellation of Lyra. Such nebulae are formed by a starburst – ionized gas has expelled into the surrounding interstellar medium by a star to form a vast luminous envelope containing the star in its last stages of its evolution before becoming a white dwarf.