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.
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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.
Contents
Characteristics
M15 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. M15 also contains Pease 1, the first planetary nebula discovered within a globular cluster[11] in 1928. 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.
Images
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The central square arcminute of M15 imaged using the lucky imaging technique
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M15Hunter.jpg
Messier 15 with amateur telescope
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M15map.png
Map showing the location of M15
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M15 Globular Cluster from the Mount Lemmon SkyCenter Schulman Telescope courtesy Adam Block.jpg
Deep Broadband (RGB) image of M15 from the Mount Lemmon SkyCenter
See also
References
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- ↑ Lua error in package.lua at line 80: module 'strict' not found. Mass is from MPD on Table 1.
- ↑ distance × sin( diameter_angle / 2 ) = 88 ly radius
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- ↑ 9.0 9.1 9.2 9.3 http://www.astropix.com/HTML/SHOW_DIG/M15_Pease1.HTM
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ http://messier.seds.org/more/m015_h2.html
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External links
Wikimedia Commons has media related to Messier 15. |
- 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
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- Messier 15 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images