< Messier Index
M15

M15 photographed by Hubble Space Telescope. 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 -
Notable features steep central cusp
Other designations NGC 7078, GCl 120[1]

Messier 15 or M15 (also designated NGC 7078) is a w:globular cluster in the w:constellation Pegasus. It was discovered by w:Jean-Dominique Maraldi in w:1746 and included in w:Charles Messier's catalogue of w:comet-like objects in w:1764. At an estimated 13.2 billion years old, it is one of the oldest known globular clusters.

M15 is about 33,600 w:light-years from w:Earth. It has an w:absolute magnitude of -9.2 which translates to a total w:luminosity of 360,000 times that of the w:Sun. Messier 15 is one of the most densely packed globulars known in the w:Milky Way galaxy. Its core has undergone a contraction known as 'w:core collapse' and it has a central density cusp with an enormous number of stars surrounding what may be a central black hole.

Messier 15 contains 112 w:variable stars, a rather high number. It also contains at least 8 w:pulsars, including one double w:neutron star system, M15 C. Moreover, M15 houses w:Pease 1, one of only four w:planetary nebulae known to reside within a globular cluster, which was discovered in w:1928.

To the amateur w:astronomer Messier 15 appears as a fuzzy star in the smallest of w: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.

References

  1. 1 2 3 "SIMBAD Astronomical Database". Results for NGC 7078. http://simbad.u-strasbg.fr/Simbad. Retrieved 2006-11-16.
  2. ↑ distance × sin( diameter_angle / 2 ) = 88 ly. radius
 
Messier Index
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 • M104 • M105 • M106 • M107 • M108 • M109 • M110
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