Astronomy Picture of the Day

Explanation: A familiar sight for northern hemisphere astronomers, the Ring Nebula (M57) is some 2,000 light-years away in the musical constellation Lyra. The central ring is about one light-year across, but this remarkably deep exposure - a collaborative effort combining data from two different telescopes - explores the looping filaments of glowing gas extending much farther from the nebula's central star. Of course, in this well-studied example of a planetary nebula, the glowing material does not come from planets. Instead, the gaseous shroud represents outer layers expelled from a dying, sun-like star. This composite image includes over 16 hours of narrow-band data intended to record the red emission from hydrogen atoms, but the pronounced blue/green colour is due to emission from oxygen atoms at higher temperatures within the ring. The much more distant spiral galaxy IC 1296 is also visible at the upper right.