The Sharpless catalog is a collection of astronomical objects, specifically emission nebulae, compiled by astronomer David Sharpless in 1959. It includes 313 objects located primarily in the northern hemisphere and is widely used by astronomers for research and observation. Each entry in the catalog is designated with the prefix "Sh" followed by a number, such as Sh 2-1. The catalog helps astronomers identify and study these nebulae, which are regions of gas and dust where new stars are often born.