Centaurus A

Centaurus A

Centaurus A (NGC 5128)
Observation data (J2000 epoch)
Constellation Centaurus
Right ascension 13h 25m 27.6s[1]
Declination −43° 01′ 09″[1]
Redshift 547 ± 5 km/s[1]
Distance 10–16 Mly (3–5 Mpc)[2][3][4][5][6]
Type S0 pec[1] or Ep[7]
Size (ly) 60,000 ly[8]
Apparent dimensions (V) 25′.7 × 20′.0[1]
Apparent magnitude (V) 6.84[9][10]
Notable features Unusual dust lane
Other designations
NGC 5128,[1] Arp 153,[1] PGC 46957,[1] 4U 1322–42,[11] Caldwell 77

Centaurus A or NGC 5128 is a prominent galaxy in the constellation of Centaurus. It was discovered in 1826 by Scottish astronomer James Dunlop from his home in Parramatta, in New South Wales, Australia. There is considerable debate in the literature regarding the galaxy's fundamental properties such as its Hubble type (lenticular galaxy or a giant elliptical galaxy)[7] and distance (10–16 million light-years).[2][3][4][5][6] NGC 5128 is one of the closest radio galaxies to Earth, so its active galactic nucleus has been extensively studied by professional astronomers.[12] The galaxy is also the fifth brightest in the sky,[12] making it an ideal amateur astronomy target,[13] although the galaxy is only visible from low northern latitudes and the southern hemisphere.

The center of the galaxy contains a supermassive black hole with a mass equivalent to 55 million solar masses,[14] which ejects a relativistic jet that is responsible for emissions in the X-ray and radio wavelengths. By taking radio observations of the jet separated by a decade, astronomers have determined that the inner parts of the jet are moving at about one half of the speed of light. X-rays are produced farther out as the jet collides with surrounding gases resulting in the creation of highly energetic particles. The X-ray jets of Centaurus A are thousands of light-years long, while the radio jets are over a million light-years long.[15]

Like other starburst galaxies, a collision is suspected to be responsible for the intense burst of star formation. Models have suggested that Centaurus A was a large elliptical galaxy which collided and merged with a smaller spiral galaxy.[16]

Morphology

Centaurus A may be described as having a peculiar morphology. As seen from Earth, the galaxy looks like a lenticular or elliptical galaxy with a superimposed dust lane.[17] The peculiarity of this galaxy was first identified in 1847 by John Herschel, and the galaxy was included in Halton Arp's Atlas of Peculiar Galaxies (published in 1966) as one of the best examples of a "disturbed" galaxy with dust absorption.[18] The galaxy's strange morphology is generally recognized as the result of a merger between two smaller galaxies.[19]

Schematic diagram of the components of the Centaurus A galaxy

The bulge of this galaxy is composed mainly of evolved red stars.[17] The dusty disk, however, has been the site of more recent star formation;[12] over 100 star formation regions have been identified in the disk.[20]

Overview of the radio structure of Centaurus A

Supernova

Two supernovae have been detected in Centaurus A.[21] The first supernova, named SN 1986G, was discovered within the dark dust lane of the galaxy by R. Evans in 1986.[22] It was later identified as a type Ia supernova,[23] which forms when a white dwarf's mass grows large enough to ignite carbon fusion in its center, touching off a runaway thermonuclear reaction, as may happen when a white dwarf in a binary star system strips gas away from the other star. SN 1986G was used to demonstrate that the spectra of type Ia supernovae are not all identical, and that type Ia supernovae may differ in the way that they change in brightness over time.[23]

The second supernova, dubbed SN2016adj[24] was discovered by Backyard Observatory Supernova Search in February 2016.[25]

Distance

Distance estimates to NGC 5128 established since the 1980s typically range between 3–5 Mpc.[2][3][4][5][6][26] Classical Cepheids discovered in the heavily-obscured dust lane of NGC 5128 yield a distance between ~3–3.5 Mpc, depending on the nature of the extinction law adopted and other considerations.[4][5] Mira variables[26] and Type II Cepheids[4][5] were also discovered in NGC 5128, the latter being rarely detected beyond the Local Group.[27] The distance to NGC 5128 established from several indicators such as Mira variables and planetary nebulae favour a more distant value of ~3.8 Mpc.[7][6]

Nearby galaxies and galaxy group information

Centaurus A is at the center of one of two subgroups within the Centaurus A/M83 Group, a nearby group of galaxies.[28] Messier 83 (the Southern Pinwheel Galaxy) is at the center of the other subgroup. These two groups are sometimes identified as one group[29][30] and sometimes identified as two groups.[31] However, the galaxies around Centaurus A and the galaxies around M83 are physically close to each other, and both subgroups appear not to be moving relative to each other.[32] The Centaurus A/M83 Group is located in the Virgo Supercluster.

Visibility

Elliptical galaxy Centaurus A and its strange globular clusters[33]

Centaurus A is located approximately 4° north of Omega Centauri (a globular cluster visible with the naked eye).[13] Because the galaxy has a high surface brightness and relatively large angular size, it is an ideal target for amateur astronomy observations. The bright central bulge and dark dust lane are visible even in finderscopes and large binoculars,[13] and additional structure may be seen in larger telescopes.[13] Centaurus A is visible to the naked eye under exceptionally good conditions.[34]

Gallery

  1. ^ "Firestorm of Star Birth in Galaxy Centaurus A". NASA. Retrieved 27 September 2012. 

See also

References

  1. 1 2 3 4 5 6 7 8 "NASA/IPAC Extragalactic Database". Results for Centaurus A. Retrieved 2006-12-06.
  2. 1 2 3 J. L. Tonry; A. Dressler; J. P. Blakeslee; E. A. Ajhar; et al. (2001). "The SBF Survey of Galaxy Distances. IV. SBF Magnitudes, Colors, and Distances". Astrophysical Journal 546 (2): 681–693. arXiv:astro-ph/0011223. Bibcode:2001ApJ...546..681T. doi:10.1086/318301.
  3. 1 2 3 "Distance Results for NGC 5128". NASA/IPAC Extragalactic Database. Retrieved 2010-04-26.
  4. 1 2 3 4 5 Ferrarese Laura; Mould Jeremy R.; Stetson Peter B.; Tonry John L.; et al. (2007). "The Discovery of Cepheids and a Distance to NGC 5128". The Astrophysical Journal 654: 186. arXiv:astro-ph/0605707. Bibcode:2007ApJ...654..186F. doi:10.1086/506612.
  5. 1 2 3 4 5 Majaess, D. (2010). "The Cepheids of Centaurus A (NGC 5128) and Implications for H0". Acta Astronomica 60: 121. arXiv:1006.2458. Bibcode:2010AcA....60..121M.
  6. 1 2 3 4 Harris, Gretchen L. H.; Rejkuba, Marina; Harris, William E. (2010). "The Distance to NGC 5128 (Centaurus A)". Publications of the Astronomical Society of Australia 27 (4): 457–462. arXiv:0911.3180. Bibcode:2010PASA...27..457H. doi:10.1071/AS09061.
  7. 1 2 3 Harris, Gretchen L. H. (2010). "NGC 5128: The Giant Beneath". Publications of the Astronomical Society of Australia 27 (4): 475. arXiv:1004.4907. Bibcode:2010PASA...27..475H. doi:10.1071/AS09063.
  8. ↑ http://apod.nasa.gov/apod/ap120404.html
  9. ↑ "SIMBAD-A". SIMBAD Astronomical Database. Retrieved 2009-11-29.
  10. ↑ Armando, Gil de Paz; Boissier; Madore; Seibert; Boselli; et al. (2007). "The GALEX Ultraviolet Atlas of Nearby Galaxies". Astrophysical Journal Supplement 173 (2): 185–255. arXiv:astro-ph/0606440. Bibcode:2007ApJS..173..185G. doi:10.1086/516636.
  11. ↑ 4U catalog browse version.
  12. 1 2 3 F. P. Israel (1998). "Centaurus A – NGC 5128". Astronomy and Astrophysics Review 8 (4): 237–278. arXiv:astro-ph/9811051. Bibcode:1998A&ARv...8..237I. doi:10.1007/s001590050011.
  13. 1 2 3 4 D. J. Eicher (1988). The Universe from Your Backyard. Cambridge: Cambridge University Press. ISBN 0-521-36299-7.
  14. ↑ "Radio Telescopes Capture Best-Ever Snapshot of Black Hole Jets". NASA. Retrieved 2012-10-02.
  15. ↑ "Astronomy Picture of the Day – Centaurus Radio Jets Rising". NASA. 2011-04-13. Retrieved 2011-04-16.
  16. ↑ Quillen, A. C.; Brookes, M. H.; Keene, J.; Stern, D.; Lawrence, C. R.; Werner, M. W. (2006). "Spitzer Observations of the Dusty Warped Disk of Centaurus A". The Astrophysical Journal 645 (2): 1092. arXiv:astro-ph/0601135. Bibcode:2006ApJ...645.1092Q. doi:10.1086/504418.
  17. 1 2 A. Sandage; J. Bedke (1994). Carnegie Atlas of Galaxies. Washington, D.C.: Carnegie Institution of Washington. ISBN 0-87279-667-1.
  18. ↑ H. Arp (1966). "Atlas of Peculiar Galaxies". Astrophysical Journal Supplement 14: 1–20. Bibcode:1966ApJS...14....1A. doi:10.1086/190147.
  19. ↑ W. Baade; R. Minkowski (1954). "On the Identification of Radio Sources". Astrophysical Journal 119: 215–231. Bibcode:1954ApJ...119..215B. doi:10.1086/145813.
  20. ↑ P. W. Hodge; R. C. Kennicutt Jr. (1982). "An atlas of H II regions in 125 galaxies". Astrophysical Journal 88: 296–328. Bibcode:1983AJ.....88..296H. doi:10.1086/113318.
  21. ↑ "NASA/IPAC Extragalactic Database". Results for extended name search on Centaurus A. Retrieved 2007-03-07.
  22. ↑ R. Evans; R. H. McNaught; C. Humphries (1986). "Supernova 1986G in NGC 5128". IAU Circular 4208: 1. Bibcode:1986IAUC.4208....1E.
  23. 1 2 M. M. Phillips; A. C. Phillips; S. R. Heathcote; V. M. Blanco; et al. (1987). "The type 1a supernova 1986G in NGC 5128 – Optical photometry and spectra". Publications of the Astronomical Society of the Pacific 99: 592–605. Bibcode:1987PASP...99..592P. doi:10.1086/132020.
  24. ↑
  25. ↑
  26. 1 2 Rejkuba, M. (2004). "The distance to the giant elliptical galaxy NGC 5128". Astronomy and Astrophysics 413 (3): 903. arXiv:astro-ph/0310639. Bibcode:2004A&A...413..903R. doi:10.1051/0004-6361:20034031.
  27. ↑ Majaess, D.; Turner, D.; Lane, D. (2009). "Type II Cepheids as Extragalactic Distance Candles". Acta Astronomica 59: 403. arXiv:0909.0181. Bibcode:2009AcA....59..403M.
  28. ↑ I. D. Karachentsev; M. E. Sharina; A. E. Dolphin; E. K. Grebel; et al. (2002). "New distances to galaxies in the Centaurus A group". Astronomy and Astrophysics 385 (1): 21–31. Bibcode:2002A&A...385...21K. doi:10.1051/0004-6361:20020042.
  29. ↑ R. B. Tully (1988). Nearby Galaxies Catalog. Cambridge: Cambridge University Press. ISBN 0-521-35299-1.
  30. ↑ P. Fouque; E. Gourgoulhon; P. Chamaraux; G. Paturel (1992). "Groups of galaxies within 80 Mpc. II – The catalogue of groups and group members". Astronomy and Astrophysics Supplement 93: 211–233. Bibcode:1992A&AS...93..211F.
  31. ↑ A. Garcia (1993). "General study of group membership. II – Determination of nearby groups". Astronomy and Astrophysics Supplement 100: 47–90. Bibcode:1993A&AS..100...47G.
  32. ↑ I. D. Karachentsev (2005). "The Local Group and Other Neighboring Galaxy Groups". Astronomical Journal 129 (1): 178–188. arXiv:astro-ph/0410065. Bibcode:2005AJ....129..178K. doi:10.1086/426368.
  33. ↑ "The Dark Side of Star Clusters". Retrieved 12 June 2015.
  34. ↑ http://astronomy-mall.com/Adventures.In.Deep.Space/aintno.htm

External links

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Coordinates: 13h 25m 27.6s, −43° 01′ 09″

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