NGC 253

Lore & Background

The Sculptor Galaxy was discovered by Caroline Herschel in 1783 during her systematic comet searches. John Herschel later observed it with an 18-inch metallic mirror reflector at the Cape of Good Hope, describing it as 'very bright and large (24′ in length); a superb object.... Its light is somewhat streaky, but I see no stars in it except 4 large and one very small one.' In 1961, Allan Sandage noted it as the prototype of a special subgroup of Sc systems, where dust patterns dominate the photographic images and spiral arms are often difficult to trace. Bernard Y. Mills discovered that it is also a fairly strong radio source. The Hubble Space Telescope took a detailed image of NGC 253 in 1998.

The galaxy lies at the center of the Sculptor Group, one of the nearest galaxy groups to the Milky Way, and is the brightest member. Its starburst has produced several super star clusters in its center, including one with a mass of solar masses and absolute magnitude at least −15, and others with masses around solar masses. The starburst is thought to have been triggered by a collision with a gas-rich dwarf galaxy about 200 million years ago. A superwind from massive stars and supernovae has blown material into the galaxy's halo, possibly inhibiting further star formation. Only one supernova, SN 1940E, has been detected within the galaxy, discovered by Fritz Zwicky in 1940. The first confirmed nova, AT 2024pid, was discovered by BlackGEM in July 2024. A supermassive black hole at the center has an estimated mass of 5 million solar masses.

Reader's Guide

NGC 253 is significant as one of the brightest and most easily viewed spiral galaxies in the sky after the Andromeda Galaxy, visible through binoculars and even reportedly with the unaided eye under exceptional conditions. It serves as a prototype for a subgroup of Sc galaxies dominated by dust patterns, as described by Allan Sandage. Its status as a starburst galaxy makes it a key object for studying intense star formation, super star clusters, and the effects of galactic superwinds. The galaxy is also notable for its large system of satellite galaxies, with discoveries continuing into the 2020s, including faint dwarf galaxies identified by amateur and professional astronomers. The Hubble Space Telescope has provided detailed imagery, and the Very Large Telescope's MUSE instrument has also observed it. Its proximity and brightness make it a frequent target for both amateur observers and professional research into galaxy evolution and starburst phenomena.

Did You Know?

• It is one of the intrinsically brightest galaxies near the Milky Way, surpassed only by the Andromeda Galaxy and the Sombrero Galaxy.
• Only one supernova, SN 1940E, has been detected in the Sculptor Galaxy, discovered by Fritz Zwicky in 1940.
• The galaxy's central supermassive black hole has an estimated mass of 5 million solar masses, slightly heavier than Sagittarius A*.