Planetary nebulae such as the famous Ring Nebula, M57, are so named because early observers believed that through the telescope they resembled the gas giant planets of our solar system, such as Jupiter, Uranus and Neptune. M57, in fact, appears slightly larger than Jupiter, and is perhaps the best known of the planetary nebulae visible from earth.

Planetary nebulae consist of shells of gas blown off from old, very hot stars near the end of their lives. At the center of M57 is the small, extremely hot core of the star that formed the nebula - it is barely visible in this photo, which is a composite of twelve 30 second exposures made with a Canon Digital Rebel XT at the prime focus of my 203mm f/5 reflector. The photo was made on the morning of June 10, 2007.

Recent photos of M57 made by the Hubble space telescope indicate that it is actually shaped like a cylinder, and that it appears to us as a ring because we are seeing it nearly end-on. It is believed to be around 2,000 light years from earth, and the central star is probably planet-sized, with a surface temperature in excess of 200,000 degrees Fahrenheit. Intense ultraviolet radiation emitted by the central star causes the gaseous, cast-off shell to glow similar to the way a neon light tube glows.