|Observation data (J2000 epoch)|
|Right ascension||21h 29m 58.33s|
|Declination||+12° 10′ 01.2″|
|Distance||33 kly (10 kpc)|
|Apparent magnitude (V)||+6.2|
|Apparent dimensions (V)||18′.0|
|Estimated age||12.0 Gyr|
|Notable features||steep central cusp|
|Other designations||NGC 7078, GCl 120|
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 1
- Amateur astronomy 2
- X-ray sources 3
- Images 4
- See also 5
- References 6
- External links 7
M15 is about 33,600 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. M15 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.
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 diameter) will start to reveal individual stars, the brightest of which are of magnitude +12.6. The cluster appears 18 arc minutes in size.
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.
The central square arcminute of M15 imaged using the lucky imaging technique
- Shapley, Harlow; Sawyer, Helen B. (August 1927). "A Classification of Globular Clusters". Harvard College Observatory Bulletin 849 (849): 11–14.
- 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.
- 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.
- Marks, Michael; Kroupa, Pavel (August 2010). "Initial conditions for globular clusters and assembly of the old globular cluster population of the Milky Way". 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.
- 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.
- "SIMBAD Astronomical Database". Results for NGC 7078. Retrieved 2006-11-16.
- Gerssen, J; van der Marel, R P; Gebhardt, K; Guhathakurta, P; Peterson, R C; Pryor, C (2003). Evidence for an Intermediate-Mass Black Hole in the Globular Cluster M15. II. Kinematic Analysis and Dynamical Modeling"Hubble Space Telescope" (PDF).
- Cohen, J. G.; Gillett, F. C. (1989). "The peculiar planetary nebula in M22".
- Forman W; Jones C; Cominsky L; Julien P; Murray S; Peters G (1978). "The fourth Uhuru catalog of X-ray sources".
- White NE; Angelini L (2001). "The discovery of a second luminous low-mass X-ray binary in the globular cluster M15".
- 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.
- Messier 15 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images