Sculptor Galaxy

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Sculptor Galaxy

The Sculptor Galaxy as seen at near-infrared wavelengths. Credit: 2MASS. North is up.
Observation data (J2000 epoch)
Constellation Sculptor
Right ascension 00h 47m 33s[1]
Declination -25° 17′ 18″[1]
Redshift 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] NGC 253,[1] UGCA 13,[1] PGC 2789[1]
See also: Galaxy, List of galaxies

The Sculptor Galaxy (NGC 253) 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.

Contents

[edit] Observational history

The galaxy was discovered by Caroline Herschel in 1783 while doing one of her systematic comet searches.[3][4] About a half century later, John Herschel while at the Cape of Good Hope observed it using his 18 inch metallic mirror reflector.[4] He then 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..."[4]

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."[5] B. Y. Mills, working out of Sydney, discovered that the Sculptor Galaxy is also a fairly strong radio source.[4]

In 1998 the hubble space telescope took a close up of NGC 253.[6]

A Hubble Space Telescope (HST) close up view of NGC 253. Credit: HST/NASA/ESA.
A Hubble Space Telescope (HST) close up view of NGC 253. Credit: HST/NASA/ESA.

[edit] Supernovae

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 50′ southwest of the galaxy's nucleus[7]. It was discovered on November 1940[7].

[edit] Recent distance estimates

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).[8][9]

Combining the most reliable distance estimates to get a weighted average gives a distance of 11.4 ± 0.7 Mly (3.5 ± 0.2 Mpc).[2]

[edit] Galaxy group information

The Sculptor Galaxy is located at the center of the Sculptor Group, which is one of the nearest groups of galaxies to the Milky Way[10] The Sculptor Galaxy, which is the brightest galaxy in this 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.[11][10]

[edit] Amateur observation

[edit] Observations with binoculars

As one of the brightest galaxies in the sky, the Sculptor Galaxy is viewable through binoculars. It is considered to be one of the most easily viewed galaxies in the sky after the Andromeda Galaxy[12][4]

[edit] Observations with amateur telescopes

The Sculptor Galaxy is a good target for observation with a telescope with a 300 mm diameter or larger.[12] As seen through such telescopes, it appears as a galaxy with a long, oval bulge and a mottled disk.[12] Although the bulge appears only slightly brighter than the rest of the galaxy, it is fairly extended compared to the disk.[12] In 400 mm scopes and larger, a dark dust lane northwest of the nucleus is visible, and over a dozen faint stars may be seen superimposed on the bulge.[12]

[edit] External links

[edit] See also

  • Globular cluster NGC 288 is located 1°.8 south-southeast of the Sculptor Galaxy.

[edit] References

  1. ^ a b c d e f g h i j k NASA/IPAC Extragalactic Database. Results for extended name search on NGC 253. Retrieved on 2006-11-25.
  2. ^ a b c Rekola, R.; Richer, M. G.; McCall, Marshall L.; Valtonen, M. J.; Kotilainen, J. K.; Flynn, Chris (2005). "Distance to NGC 253 based on the planetary nebula luminosity function". Monthly Notices of the Royal Astronomical Society 361 (1): 330-336. doi:10.1111/j.1365-2966.2005.09166.x. 
  3. ^ Dreyer, J. L. E. (1888). "A New General Catalogue of Nebulae and Clusters of Stars,being the Catalogue of the late Sir John F.W. Herschel, Bart., revised, corrected, and enlarged.". Memoirs of the Royal Astronomical Society 49: 1-237. 
  4. ^ a b c d e Burnham, Robert (1978). Burnham's Celestial Handbook; An Observers Guide to the Universe Beyond the Solar System; Volume Three, Pavo Through Vulpecula. Dover Publications, Inc., 1736. ISBN 0-486-24065-7. 
  5. ^ Sandage, Allan (1961). The Hubble atlas of galaxies. Washington: Carnegie Institution. 
  6. ^ HubbleSite NewsCenter. Results for NGC 253. Retrieved on 2007-04-05.
  7. ^ a b R. Barbon, E. Cappellaro, F. Ciatti, M. Turatto, C. T. Kowal (1984). "A revised supernova catalogue". Astronomy & Astrophysics Supplement Series 58: 735-750. 
  8. ^ I. D. Karachentsev, V. E. Karachentseva, W. K. Hutchmeier, D. I. Makarov (2004). "A Catalog of Neighboring Galaxies". Astronomical Journal 127: 2031-2068. doi:10.1086/382905. 
  9. ^ Karachentsev, I. D.; Kashibadze, O. G. (2006). "Masses of the local group and of the M81 group estimated from distortions in the local velocity field". Astrophysics 49 (1): 3-18. doi:10.1007/s10511-006-0002-6. 
  10. ^ a b I. D. Karachentsev (2005). "The Local Group and Other Neighboring Galaxy Groups". Astronomical Journal 129: 178-188. doi:10.1086/426368. 
  11. ^ I. D. Karachentsev, E. K. Grebel, M. E. Sharina, A. E. Dolphin, D. Geisler, P. Guhathakrta, P. W. Hodge, V. E. Karachentseva, A. Sarajedini, P. Seitzer (2003). "Distances to nearby galaxies in Sculptor". Astronomy and Astrophysics 404: 93-111. doi:10.1051/0004-6361:20030170. 
  12. ^ a b c d e Kepple, George Robert; Glen W. Sanner (1998). The Night Sky Observer's Guide, Volume 2. Willmann-Bell, Inc., 365, 371. ISBN 0-943396-60-3.