| Sculptor Galaxy | |
|---|---|
The Sculptor Galaxy taken with the ESO VISTA telescope at the Paranal Observatory in Chile. |
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| Observation data (J2000 epoch) | |
| Constellation | Sculptor |
| Right ascension | 00h 47m 33s[1] |
| Declination | -25° 17′ 18″[1] |
| Redshift | 0.000811[1] |
| Helio radial velocity | 243 ± 2 km/s [1] |
| Distance | 11.4 ± 0.7 Mly (3.5 ± 0.2 Mpc)[2] |
| Type | SAB(s)c[1] |
| Apparent dimensions (V) | 27′.5 × 6′.8[1] |
| Apparent magnitude (V) | 8.0[1] |
| Other designations | |
| Silver Coin Galaxy,[1] Silver Dollar Galaxy,[3] NGC 253,[1] UGCA 13,[1] PGC 2789[1] Caldwell 65[4] | |
| See also: Galaxy, List of galaxies | |
The Sculptor Galaxy (also known as the Silver Coin or Silver Dollar Galaxy, NGC 253, or Caldwell 65) is an intermediate spiral galaxy in the constellation Sculptor. The Sculptor Galaxy is a starburst galaxy, which means that it is currently undergoing a period of intense star formation.
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The galaxy was discovered by Caroline Herschel in 1783 during one of her systematic comet searches.[5][6] About half a century later, John Herschel observed it using his 18 inch metallic mirror reflector at the Cape of Good Hope.[6] He wrote, "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, and these seem not to belong to it, there being many near..."[6]
In 1961 Allan Sandage wrote in the Hubble Atlas of Galaxies that the Sculptor Galaxy is "the prototype example of a special subgroup of Sc systems....photographic images of galaxies of the group are dominated by the dust pattern. Dust lanes and patches of great complexity are scattered throughout the surface. Spiral arms are often difficult to trace.... The arms are defined as much by the dust as by the spiral pattern."[7] B. Y. Mills, working out of Sydney, discovered that the Sculptor Galaxy is also a fairly strong radio source.[6]
In 1998 the Hubble Space Telescope took a detailed image of NGC 253.[8]
Although supernovae are generally associated with starburst galaxies, only one supernova has been detected within the Sculptor Galaxy.[1] The supernova, named SN 1940E, is located approximately 54″ southwest of the galaxy's nucleus.[9] It was discovered in November 1940.[9]
At least two techniques have been used to measure distances to Sculptor in the past ten years.
Using the planetary nebula luminosity function method, an estimate of 10.89 +0.85
−1.24 Mly (3.34 +0.26
−0.38 Mpc) was achieved in 2006.[2]
Sculptor is close enough that the tip of the red giant branch (TRGB) method may also be used to estimate its distance. The estimated distance to Sculptor using this technique in 2004 yielded 12.8 ± 1.2 Mly (3.94 ± 0.37 Mpc).[10][11]
A weighted average of the most reliable distance estimates gives a distance of 11.4 ± 0.7 Mly (3.5 ± 0.2 Mpc).[2]
The Sculptor Galaxy is located at the center of the Sculptor Group, one of the nearest groups of galaxies to the Milky Way.[12] The Sculptor Galaxy (the brightest galaxy in the group) and the companion galaxies NGC 247, PGC 2881, PGC 2933, Sculptor-dE1, and UGCA 15 form a gravitationally bound core near the center of the group. Most other galaxies associated with the Sculptor Group are only weakly gravitationally bound to this core.[12][13]
As one of the brightest galaxies in the sky, the Sculptor Galaxy can be seen through binoculars. It is considered one of the most easily viewed galaxies in the sky after the Andromeda Galaxy.[6][14]
The Sculptor Galaxy is a good target for observation with a telescope with a 300 mm diameter or larger.[14] In such telescopes, it appears as a galaxy with a long, oval bulge and a mottled disk.[14] Although the bulge appears only slightly brighter than the rest of the galaxy, it is fairly extended compared to the disk.[14] In 400 mm scopes and larger, a dark dust lane northwest of the nucleus is visible, and over a dozen faint stars can be seen superimposed on the bulge.[14]
In the American television series The Event, the episode "Inostranka" reveals that the earthbound extraterrestrials originate from the Sculptor Galaxy.
Coordinates: 00h 47m 33s, −25° 17′ 18″
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