of , and surrounding nebula estimated to have been expanding for between 1,280 and 1,600 years, The nebula was discovered by Ralph Copeland in 1884. The Necklace Nebula—originally a close binary, one component of which swallowed the other as it expanded to become a giant star. The smaller star remained in orbit inside the larger, whose rotation speed increased greatly, resulting in it flinging its outer layers off into space, forming a ring with knots of bright gas formed from clumps of stellar material. It was discovered in 2005 and is around 2 light-years wide. It has a size of . Both nebulae are around from Earth. See also Sagitta (Chinese astronomy) Notes References External links The Deep Photographic Guide to the Constellations: Sagitta Warburg Institute Iconographic Database (medieval and early modern images of Sagitta) Bayer's Uranometria, from the Linda Hall Library digital collection. Constellations Northern constellations Constellations listed by Ptolemy Articles containing video clips