Omega Centauri
From Wikipedia, the free encyclopedia
| ω Centauri | |
 Omega Centauri, a large globular cluster in the constellation Centaurus. |
|
| Observation data (J2000 epoch) | |
|---|---|
| Class | Globular Cluster |
| Constellation | Centaurus |
| Right ascension | 13h 26m 45.89s[1] |
| Declination | -47° 28′ 36.7″[1] |
| Distance | 18.3 ± 1.1 kly[2] (5.6 ± 0.3 kpc) |
| Apparent magnitude (V) | 3.7[3] |
| Apparent dimensions (V) | 36′.3 |
| Physical characteristics | |
| Mass | ~1•1037 kg (~5 000 000[4] M ) |
| Radius | 97 ± 6 ly[5] |
| Estimated age | ~12 Gyr[6] |
| Other designations | NGC 5139,[1] GCl 24,[1] ω Centauri[2] |
| See also: Globular cluster, List of globular clusters | |
Omega Centauri had been listed in Ptolemy's catalog 2000 years ago as a star. Lacaille included it in his catalog as number I.5. Omega Centauri or NGC 5139 is a globular cluster of stars seen in the constellation of Centaurus, discovered by Edmond Halley in 1677 listed it as a Nebula. The English astronomer John William Herschel recognized it first as a globular cluster in the 1830s[7]. It orbits our galaxy, the Milky Way. One of the few that can be seen with the naked eye, it is both the brightest and the largest known globular cluster associated with the Milky Way. Omega Centauri is located about 18,300 light-years (5,600 pc) from Earth and contains several million Population II stars. The stars in its center are so crowded that they are believed to be only 0.1 light years away from each other. It is about 12 billion years old.
Though it is not a star, Omega Centauri was given a Bayer designation. Unlike other globular clusters, it contains several generations of stars. It has been speculated that Omega Centauri may be the core of a dwarf galaxy several hundred times its present size, which was ripped apart and absorbed by our Milky Way galaxy. Omega Centauri's chemistry and motion in the galaxy is also consistent with this picture. According to new results by the Hubble Space Telescope and the Gemini Observatory, scientists seem to have found an explanation for peculiarities: a black hole at its centre with about 40,000 solar masses. This would also foster the theory that Omega Centauri is a dwarf galaxy[8].
Like Mayall II, Omega Centauri has a range of metallicities and stellar ages which hints that it did not all form at once (as globular clusters are thought to form) and may in fact be the remains of the core of a smaller galaxy long since captured into the Milky Way. [9]
[edit] See also
[edit] External links
- Hubblesite - Peering into the core of a globular cluster
- Omega Centauri: Former Core of a Dwarf Galaxy?
- Omega Centauri: Proud Cluster or Sad Remnant?
- Omega Centauri at ESA/Hubble
- Omega Centauri on Wikisky.org
[edit] References
- ^ a b c d SIMBAD Astronomical Database. Results for NGC 5139. Retrieved on 2006-11-16.
- ^ a b van de Ven, G.; van den Bosch, R. C. E.; Verolme, E. K.; de Zeeuw, P. T. (January II 2006). "The dynamical distance and intrinsic structure of the globular cluster ω Centauri". Astronomy and Astrophysics 445 (2): 513-543.
- ^ Omega Centauri - Britannica Online Encyclopedia
- ^ Globular cluster NGC 5139
- ^ distance × sin( diameter_angle / 2 ) = 97 ± 6 kly. radius
- ^ "Peering into the Core of a Globular Cluster"[1]
- ^ Black Hole found in enigmatic Omega Centauri
- ^ Hubble Information Center (2008-04-02). "News Release - heic0809: Black hole found in enigmatic Omega Centauri". Press release. Retrieved on 2008-04-08.
- ^ Hughes, 1999, "G1 in M31 - Giant Age and Metallicity Effects in Omega Centauri I: Stromgren Photometry"
