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]
Apparent dimensions (V)	25′.7 × 20′.0[1]
Apparent magnitude (V)	6.84[8][9]
Notable features	Unusual dust lane
Other designations
NGC 5128,[1] Arp 153,[1] PGC 46957,[1] 4U 1322-42 [10]
See also: Galaxy, List of galaxies

Centaurus A (also known as NGC 5128) is a prominent galaxy in the constellation of Centaurus. 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.^[11] The galaxy is also the fifth brightest in the sky,^[11] making it an ideal amateur astronomy target,^[12] although the galaxy is only visible from low northern latitudes and the southern hemisphere.

A relativistic jet which extracts energy from the vicinity of what is believed to be a supermassive black hole at the center of the galaxy 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 radio jets of Centaurus A are over a million light years long.^[13]

As observed in other starburst galaxies, a collision is responsible for the intense burst of star formation. Using the Spitzer Space Telescope astronomers confirm that Centaurus A is going through a galaxy collision by devouring a spiral galaxy.

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.^[14] The peculiarity of this galaxy was first identified in 1847 by John Herschel, and the galaxy was included in the Atlas of Peculiar Galaxies (published in 1966) as one of the best examples of a "disturbed" galaxy with dust absorption.^[15] The galaxy's strange morphology is generally recognized as the result of a merger between two smaller galaxies.^[16]

The bulge of this galaxy is composed mainly of evolved red stars.^[14] The dusty disk, however, has been the site of more recent star formation;^[11] over 100 star formation regions have been identified in the disk.^[17]

Supernovae

One supernova has been detected in Centaurus A.^[18] The supernova, named SN 1986G, was discovered within the dark dust lane of the galaxy by R. Evans in 1986.^[19] It was later identified as a type Ia supernova,^[20] 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.^[20]

Distance

Distance estimates to NGC 5128 established since the 1980s typically range between 3-5 Mpc.^{[2][3][4][5][6][21]} 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^[21] and Type II Cepheids^[4][5] were also discovered in NGC 5128, the latter being rarely detected beyond local group.^[22] 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.^[23] Messier 83 (the Southern Pinwheel Galaxy) is at the center of the other subgroup. These two groups are sometimes identified as one group^[24][25] and sometimes identified as two groups.^[26] 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.^[27] The Centaurus A/M83 Group is located in the Virgo Supercluster.

Amateur astronomy information

Centaurus A is located approximately 4° north of Omega Centauri (a globular cluster visible with the naked eye).^[12] 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,^[12] and additional structure may be seen in larger telescopes.^[12] Centaurus A is visible to the naked eye under exceptionally good conditions. ^[28]

Gallery

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  Composite shows ultraviolet light, which comes from young stars of Centaurus A.

• 

  A Hubble Space Telescope (HST) image of the dust disk in front of the nucleus of Centaurus A. Credit: HST/NASA/ESA.

• 

  This image of the central parts of Centaurus A reveals the parallelogram-shaped remains of a smaller galaxy that was absorbed about 200 to 700 million years ago.

• 

  The heavily-obscured inner (barred?) spiral disk at 24 μm as shown by the Spitzer IR telescope

• 

  Chandra X-Ray view of Cen A in X Rays showing one relativistic jet from the central black hole

• 

  Centaurus A in submillimeter light by APEX showing the giant radio lobes, powered by the jets. Credit ESO

• 

  A composite image showing the size of the radio glow from the galaxy Centaurus A in comparison to the full Moon.

• Video about Centaurus A jets.

See also

• Messier 87 - a giant elliptical galaxy that is also a strong radio source
• NGC 1316 - a similar lenticular galaxy that is also a strong radio source

References

1. ^ ^{a b c d e f g h} "NASA/IPAC Extragalactic Database". Results for Centaurus A. http://nedwww.ipac.caltech.edu/. Retrieved 2006-12-06. 
2. ^ ^{a b c} J. L. Tonry, A. Dressler, J. P. Blakeslee, E. A. Ajhar, A. B. Fletcher, G. A. Luppino, M. R. Metzger, C. B. Moore (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. ^ ^{a b c} "Distance Results for NGC 5128". NASA/IPAC Extragalactic Database. http://nedwww.ipac.caltech.edu/cgi-bin/nDistance?name=NGC+5128. Retrieved 2010-04-26. 
4. ^ ^{a b c d e} Ferrarese Laura, Mould Jeremy R., Stetson Peter B., Tonry John L., Blakeslee John P., Ajhar Edward A. (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. ^ ^{a b c d e} Majaess, D. (2010). "The Cepheids of Centaurus A (NGC 5128) and Implications for H0". Acta Astronomica 60: 121. Bibcode 2010AcA....60..121M. 
6. ^ ^{a b c d} 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. ^ ^{a b c} Harris, Gretchen L. H. (2010). "NGC 5128: The Giant Beneath". Publications of the Astronomical Society of Australia 27 (4): 475. Bibcode 2010PASA...27..475H. doi:10.1071/AS09063. 
8. ^ "SIMBAD-A". SIMBAD Astronomical Database. http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Centaurus+A. Retrieved 2009-11-29. 
9. ^ 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. 
10. ^ 4U catalog browse version.
11. ^ ^{a b c} 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. 
12. ^ ^{a b c d} D. J. Eicher (1988). The Universe from Your Backyard. Cambridge: Cambridge University Press. ISBN 0-521-36299-7. 
13. ^ "Astronomy Picture of the Day - Centaurus Radio Jets Rising". NASA. 2011-04-13. http://apod.nasa.gov/apod/ap110413.html. Retrieved 2011-04-16. 
14. ^ ^{a b} A. Sandage, J. Bedke (1994). Carnegie Atlas of Galaxies. Washington, D.C.: Carnegie Institution of Washington. ISBN 0-87279-667-1. 
15. ^ H. Arp (1966). "Atlas of Peculiar Galaxies". Astrophysical Journal Supplement 14: 1–20. Bibcode 1966ApJS...14....1A. doi:10.1086/190147. 
16. ^ W. Baade, R. Minkowski (1954). "On the Identification of Radio Sources". Astrophysical Journal 119: 215–231. Bibcode 1954ApJ...119..215B. doi:10.1086/145813. 
17. ^ 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. 
18. ^ "NASA/IPAC Extragalactic Database". Results for extended name search on Centaurus A. http://nedwww.ipac.caltech.edu/. Retrieved 2007-03-07. 
19. ^ R. Evans, R. H. McNaught, C. Humphries (1986). "Supernova 1986G in NGC 5128". IAU Circular 4208: 1. Bibcode 1986IAUC.4208....1E. 
20. ^ ^{a b} M. M. Phillips, A. C. Phillips, S. R. Heathcote, V. M. Blanco, D. Geisler, D. Hamilton, N. B. Suntzeff, F. J. Jablonski, J. E. Steiner, A. P. Cowley, P. Schmidtke, S. Wyckoff, J. B. Hutchings, J. Tonry, M. A. Strauss, J. R. Thorstensen, W. Honey, J. Maza, M. T. Ruiz, A. U. Landolt, A. Uomoto, R. M. Rich, J. E. Grindlay, H. Cohn, H. A. Smith, J. H. Lutz, R. J. Lavery, A. Saha (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. 
21. ^ ^{a b} "The distance to the giant elliptical galaxy NGC 5128". Astronomy and Astrophysics. arXiv:astro-ph/0310639. Bibcode 2004A&A...413..903R. doi:10.1051/0004-6361:20034031. 
22. ^ Majaess, D.; Turner, D.; Lane, D. (2009). "Type II Cepheids as Extragalactic Distance Candles". Acta Astronomica 59: 403. Bibcode 2009AcA....59..403M. 
23. ^ I. D. Karachentsev, M. E. Sharina, A. E. Dolphin, E. K. Grebel, D. Geisler, P. Guhathakurta, P. W. Hodge, V. E. Karachetseva, A. Sarajedini, P. Seitzer (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. 
24. ^ R. B. Tully (1988). Nearby Galaxies Catalog. Cambridge: Cambridge University Press. ISBN 0-521-35299-1. 
25. ^ 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. 
26. ^ 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. 
27. ^ 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. 
28. ^ http://astronomy-mall.com/Adventures.In.Deep.Space/aintno.htm

• STScI. Hubble Provides Multiple Views of How to Feed a Black Hole. Press release: Space Telescope Science Institute. March 14, 1998.
• Chandra X-Ray Observatory Photo Album Centaurus A Jet

External links

• Helmut Steinle Centaurus A project
• SEDS: Peculiar Galaxy NGC 5128
• ESA/Hubble images of Centaurus A
• NASA's APOD: The Galaxy Within Centaurus A (3/4/06)
• NASA's APOD: X-Rays from an Active Galaxy (7/5/03)
• High-resolution image of Centaurus A showing the discrete elements of galactic core
• Centaurus A at UniverseToday.com
• NGC5128 Centaurus A
• Centaurus A on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images

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