Messier 15
Messier 15 | |
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![]() M15 photographed by HST. The planetary nebula Pease 1 can be seen as a small blue object to the upper left of the core of the cluster. | |
Observation data (J2000 epoch) | |
Class | IV[1] |
Constellation | Pegasus |
Right ascension | 21h 29m 58.33s[2] |
Declination | +12° 10′ 01.2″[2] |
Distance | 33 kly (10 kpc)[3] |
Apparent magnitude (V) | +6.2 |
Apparent dimensions (V) | 18′.0 |
Physical characteristics | |
Mass | 5.6×105[4] M☉ |
Radius | ~88 ly[5] |
VHB | 15.83 |
Metallicity | = –2.37[6] dex |
Estimated age | 12.0 Gyr[7] |
Notable features | steep central cusp |
Other designations | NGC 7078, GCl 120[8] |
Messier 15 or M15 (also designated NGC 7078) is a globular cluster in the constellation Pegasus. It was discovered by Jean-Dominique Maraldi in 1746 and included in Charles Messier's catalogue of comet-like objects in 1764. At an estimated 12.0 billion years old, it is one of the oldest known globular clusters.
Characteristics
M 15 is about 33,600 light-years from Earth, and 175 light-years in diameter.[9] It has an absolute magnitude of −9.2, which translates to a total luminosity of 360,000 times that of the Sun. Messier 15 is one of the most densely packed globulars known in the Milky Way galaxy. Its core has undergone a contraction known as "core collapse" and it has a central density cusp with an enormous number of stars surrounding what may be a central black hole.[10]
Home to over 100,000 stars,[9] the cluster is notable for containing a large number of variable stars (112) and pulsars (8), including one double neutron star system, M15-C. It also contains Pease 1, the first planetary nebula discovered within a globular cluster in 1928.[11] Just three others have been found in globular clusters since then.[12]
Amateur astronomy
At magnitude 6.2, M15 approaches naked eye visibility under good conditions and can be observed with binoculars or a small telescope, appearing as a fuzzy star.[9] Telescopes with a larger aperture (at least 6 in./150 mm diameter) will start to reveal individual stars, the brightest of which are of magnitude +12.6. The cluster appears 18 arc minutes in size.[9]
X-ray sources
Earth-orbiting satellites Uhuru and Chandra X-ray Observatory have detected two bright X-ray sources in this cluster: Messier 15 X-1 (4U 2129+12) and Messier 15 X-2.[13][14] The former appears to be the first astronomical X-ray source detected in Pegasus.
Gallery
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The central square arcminute of M15 imaged using the lucky imaging technique
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Messier 15 with amateur telescope
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Map showing the location of M15
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Deep Broadband (RGB) image of M15 from the Mount Lemmon SkyCenter
See also
References
- ^ Shapley, Harlow; Sawyer, Helen B. (August 1927). "A Classification of Globular Clusters". Harvard College Observatory Bulletin. 849 (849): 11–14. Bibcode:1927BHarO.849...11S.
- ^ a b Goldsbury, Ryan; et al. (December 2010). "The ACS Survey of Galactic Globular Clusters. X. New Determinations of Centers for 65 Clusters". The Astronomical Journal. 140 (6): 1830–1837. arXiv:1008.2755. Bibcode:2010AJ....140.1830G. doi:10.1088/0004-6256/140/6/1830.
- ^ Hessels, J. W. T.; et al. (November 2007). "A 1.4 GHz Arecibo Survey for Pulsars in Globular Clusters". The Astrophysical Journal. 670 (1): 363–378. arXiv:0707.1602. Bibcode:2007ApJ...670..363H. doi:10.1086/521780.
- ^ Marks, Michael; Kroupa, Pavel (August 2010). "Initial conditions for globular clusters and assembly of the old globular cluster population of the Milky Way". Monthly Notices of the Royal Astronomical Society. 406 (3): 2000–2012. arXiv:1004.2255. Bibcode:2010MNRAS.406.2000M. doi:10.1111/j.1365-2966.2010.16813.x.
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: CS1 maint: unflagged free DOI (link) Mass is from MPD on Table 1. - ^ distance × sin( diameter_angle / 2 ) = 88 ly radius
- ^ Boyles, J.; et al. (November 2011). "Young Radio Pulsars in Galactic Globular Clusters". The Astrophysical Journal. 742 (1): 51. arXiv:1108.4402. Bibcode:2011ApJ...742...51B. doi:10.1088/0004-637X/742/1/51.
- ^ Koleva, M.; et al. (April 2008). "Spectroscopic ages and metallicities of stellar populations: validation of full spectrum fitting". Monthly Notices of the Royal Astronomical Society. 385 (4): 1998–2010. arXiv:0801.0871. Bibcode:2008MNRAS.385.1998K. doi:10.1111/j.1365-2966.2008.12908.x.
{{cite journal}}
: CS1 maint: unflagged free DOI (link) - ^ "M 15". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2006-11-16.
- ^ a b c d "M 15". astropix.
- ^ Gerssen J, van der Marel RP, Gebhardt K, Guhathakurta P, Peterson RC, Pryor C (2003). "Evidence for an intermediate-mass black hole in the globular cluster M 15. II. Kinematic analysis and dynamical modeling". Astronomical Journal. Hubble Space Telescope. 125 (1): 376–377. arXiv:astro-ph/0210158. Bibcode:2003AJ....125..376G. doi:10.1086/345574.
- ^ Cohen, J.G.; Gillett, F.C. (1989). "The peculiar planetary nebula in M 22" (PDF). Astrophysical Journal. 346: 803–807. Bibcode:1989ApJ...346..803C. doi:10.1086/168061.
- ^ "more". SEDS.org. Messier 15.
- ^ Forman W; Jones C; Cominsky L; Julien P; Murray S; Peters G (1978). "The fourth Uhuru catalog of X-ray sources". Astrophysical Journal Supplement Series. 38: 357. Bibcode:1978ApJS...38..357F. doi:10.1086/190561.
- ^ White NE; Angelini L (2001). "The discovery of a second luminous low-mass X-ray binary in the globular cluster M15". Astrophysical Journal Letters. 561 (1): L101–5. arXiv:astro-ph/0109359. Bibcode:2001ApJ...561L.101W. doi:10.1086/324561.
External links
![](http://upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/30px-Commons-logo.svg.png)
- Messier 15, SEDS Messier pages
- Messier 15, Galactic Globular Clusters Database page
- Globular Cluster Photometry With the Hubble Space Telescope. V. WFPC Study of M15's Central density Cusp
- Wikisky.org SDSS image of M15
- Gretton, Roy; Gray, Meghan. "M15 – Globular Cluster". Deep Sky Videos. Brady Haran.
- Messier 15 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images