The “Ring Nebula” (M 57) is a planetary nebula in the constellation of Lyra. The nebula is formed when a star, during the last stages of its evolution before becoming a white dwarf, expels a vast luminous envelope of ionized gas into the surrounding interstellar space. The distance is about 2.500 light-years. The shell expands at a rate of 20-30 km/s. M57 is illuminated by a central white dwarf.
Planetary Nebula M57, Vorst (D), 22 April 2020, William Optics 110 mm APO FLT f/7, Canon EOS 600D, UV-IR, UHC filter, 800 ISO, f = 770 mm, 3600 sec, PixInsight V 1.8.8-5