August 11, 2011: A giant cosmic necklace glows brightly in this NASA Hubble Space Telescope image. The object, aptly named the Necklace Nebula, is a recently discovered planetary nebula, the glowing remains of an ordinary, Sun-like star. The nebula consists of a bright ring, measuring 12 trillion miles across, dotted with dense, bright knots of gas that resemble diamonds in a necklace. The knots glow brightly due to absorption of ultraviolet light from the central stars.
The Necklace Nebula is located 15,000 light-years away in the constellation Sagitta (the Arrow). In this composite image, taken on July 2, 2011, Hubble's Wide Field Camera 3 captured the glow of hydrogen (blue), oxygen (green), and nitrogen (red).See the rest: