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Messier 15
Deep Broadband (RGB) image of M15
Observation data (J2000 epoch)
Class	IV
Constellation	Pegasus
Right ascension	21 29 58.33
Declination	+12° 10′ 01.2″
Distance	35.69 ± 0.43 kly (10.944 ± 0.131 kpc)
Apparent magnitude (V)	6.2
Apparent dimensions (V)	18′.0
Physical characteristics
Mass	5.6×10 M☉
Radius	~88 ly
VHB	15.83
Metallicity	${\displaystyle {\begin{smallmatrix}\left\end{smallmatrix}}}$ = –2.37 dex
Estimated age	12.0 Gyr
Notable features	steep central cusp
Other designations	NGC 7078, GCl 120
See also: Globular cluster, List of globular clusters

Messier 15 or M15 (also designated NGC 7078 and sometimes known as the Great Pegasus Cluster) 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 12.5±1.3 billion years old, it is one of the oldest known globular clusters.

Characteristics

M 15 is about 35,700 light-years from Earth, and 175 light-years in diameter. 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.

Home to over 100,000 stars, 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. Just three others have been found in globular clusters since then.

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. Telescopes with a larger aperture (at least 6 in. (150 mm)) will start to reveal individual stars, the brightest of which are of magnitude +12.6. The cluster appears 18 arc minutes in size (three tenths of a degree across). M15 is around 4° WNW of the brightest star of Pegasus, Epsilon Pegasi.

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. The former appears to be the first astronomical X-ray source detected in Pegasus.

Gallery

• The central square arcminute of M15 imaged using the lucky imaging technique
• Map showing the location of M15
• 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.

See also

• List of Messier objects
• X-ray astronomy

References

1. Shapley, Harlow; Sawyer, Helen B. (August 1927). "A Classification of Globular Clusters". Harvard College Observatory Bulletin. 849 (849): 11–14. Bibcode:1927BHarO.849...11S.
2. ^ 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. S2CID 119183070.
3. ^ Bhardwaj, Anupam; Rejkuba, Marina; Sloan, G. C.; Marconi, Marcella; Yang, Soung-Chul (2021). "Optical and Near-infrared Pulsation Properties of RR Lyrae and Population II Cepheid Variables in the Messier 15 Globular Cluster". The Astrophysical Journal. 922 (1): 20. arXiv:2108.11388. Bibcode:2021ApJ...922...20B. doi:10.3847/1538-4357/ac214d. S2CID 237304172.
4. "Messier 15". SEDS Messier Catalog. Retrieved 21 July 2024.
5. 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. S2CID 118652005. Mass is from M_PD on Table 1.
6. distance × sin( diameter_angle / 2 ) = 88 ly radius
7. 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. S2CID 118649860.
8. 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. S2CID 17571531.
9. "M 15". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2006-11-16.
10. O'Malley, Erin M.; Gilligan, Christina; Chaboyer, Brian (April 2017). "Absolute Ages and Distances of 22 GCs Using Monte Carlo Main-sequence Fitting". The Astrophysical Journal. 838 (2): 162. arXiv:1703.01915. Bibcode:2017ApJ...838..162O. doi:10.3847/1538-4357/aa6574. S2CID 11852378.
11. ^ "M 15". astropix.
12. 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. S2CID 118948032.
13. 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. S2CID 119770028.
14. ^ O'Meara, Stephen James; Levy, David H. (1998), Deep-Sky Companions: The Messier Objects, Cambridge University Press, p. 74, ISBN 978-0521553322.
15. "more". SEDS.org. Messier 15.
16. 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.
17. 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. S2CID 18877294.

External links

• 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

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v t e Messier objects
List	M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M11 M12 M13 M14 M15 M16 M17 M18 M19 M20 M21 M22 M23 M24 M25 M26 M27 M28 M29 M30 M31 M32 M33 M34 M35 M36 M37 M38 M39 M40 M41 M42 M43 M44 M45 M46 M47 M48 M49 M50 M51 M52 M53 M54 M55 M56 M57 M58 M59 M60 M61 M62 M63 M64 M65 M66 M67 M68 M69 M70 M71 M72 M73 M74 M75 M76 M77 M78 M79 M80 M81 M82 M83 M84 M85 M86 M87 M88 M89 M90 M91 M92 M93 M94 M95 M96 M97 M98 M99 M100 M101 M102 M103 Added M104 M105 M106 M107 M108 M109 M110
See also	Caldwell catalogue Catalogue of Nebulae and Clusters of Stars Herschel 400 Catalogue Index Catalogue New General Catalogue Revised New General Catalogue
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