Title: M57, The Ring Nebula

Source: NASA

Information: M57, the Ring Nebula in the constellation Lyra is the most famous planetary nebula. Planetary nebulae are not so named because of an association with planets but because, in a telescope, their round shape resembles a planet. The nebula is lit by fluorescence caused by the large amount of ultraviolet radiation emitted by the central star. The rate of expansion in the ring indicates that the nebula initially formed about 20,000 years ago. Planetary nebulae are not associated with novae, but are their own discreet phenomenon in the universe. It is estimated that there are over ten thousand planetary nebulae in our galaxy at this time.