Messier 15
From Wikipedia, the free encyclopedia
| Messier 15 | |
|---|---|
 M15 photographed by HST. The planetary nebula Pease 1 can be seen as a fuzzy reddish object near the upper left of this image. |
|
| Observation data (J2000 epoch) | |
| Class | IV |
| Constellation | Pegasus |
| Right ascension | 21h 29m 58.38s[1] |
| Declination | +12° 10′ 00.6″[1] |
| Distance | 33.6 kly (10.3 kpc) |
| Apparent magnitude (V) | +6.2 |
| Apparent dimensions (V) | 18′.0 |
| Physical characteristics | |
| Mass | - kg (- M ) |
| Radius | ~88 ly[2] |
| VHB | 15.83 |
| Estimated age | 13.2 Gyr |
| Notable features | steep central cusp |
| Other designations | NGC 7078, GCl 120[1] |
| See also: Globular cluster, List of globular clusters | |
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 13.2 billion years old, it is one of the oldest known globular clusters.
M15 is about 33,600 light-years from Earth. 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.[3]
Messier 15 contains 112 variable stars, a rather high number. It also contains at least 8 pulsars, including one double neutron star system, M15 C. Moreover, M15 houses Pease 1,[4] one of only four planetary nebulae known to reside within a globular cluster, which was discovered in 1928.[1]
To the amateur astronomer Messier 15 appears as a fuzzy star in the smallest of telescopes. Mid to large size telescopes (at least 6 in./150 mm diameter) will start to reveal individual stars, the brightest of which are of magnitude +12.6.
 The central square arcminute of M15 imaged using the lucky imaging technique |
 Messier 15 with amateur telescope |
 |
Wikimedia Commons has media related to: Messier 15 |
[edit] 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
- Messier 15 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images
[edit] References
- ^ a b c "SIMBAD Astronomical Database". Results for NGC 7078. http://simbad.u-strasbg.fr/Simbad. Retrieved 2006-11-16.
- ^ distance × sin( diameter_angle / 2 ) = 88 ly. radius
- ^ Gerssen, J; van der Marel, R P; Gebhardt, K; Guhathakurta, P; Peterson, R C; Pryor, C (January 2003). "Hubble Space Telescope Evidence for an Intermediate-Mass Black Hole in the Globular Cluster M15. II. Kinematic Analysis and Dynamical Modeling". The Astronomical Journal 125: 376-377. doi:. http://www.iop.org/EJ/article/1538-3881/125/1/376/209270.html.
- ^ Cohen, J. G.; Gillett, F. C. (November 15, 1989). "The peculiar planetary nebula in M22". Astrophysical Journal, Part 1 (ISSN 0004-637X), Research supported by California Institute of Technology 346: 803–807. doi:. http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1989ApJ...346..803C.
|
|||||||||||
Coordinates: 
21h 29m 58.38s, +12° 10′ 00.6″
 |
This star cluster–related article is a stub. You can help Wikipedia by expanding it. |
