NASA has released a Hubble Space Telescope image of a brightly glowing,giant cosmic necklace of a recently discovered planetary nebula,aptly named Necklace Nebula. The nebula,situated 15,000 light years away in the constellation,Sagitta,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. A pair of stars orbiting very close together produced the nebula,also called PN G054.2-03.4. About 10,000 years ago one of the aging stars ballooned to the point where it enveloped its companion star. This caused the larger star to spin so fast that much of its gaseous envelope expanded into space. Due to centrifugal force,most of the gas escaped along the stars equator,producing a dense ring. The embedded bright knots are the densest gas clumps in the ring. The stars are furiously whirling around each other,completing an orbit in a little more than a day.
