Messier Index/M15

M15 250px 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. J2000 IV Pegasus 21 29 58.38SIMBAD Astronomical Database Results for NGC 7078 http://simbad.u-strasbg.fr/Simbad 2006-11-16 +12 10 00.6 33.6 kly 10.3 kpc +6.2 18′.0 - - ~88 lydistance × sin( diameter_angle / 2 ) = 88 ly. radius 15.83 - steep central cusp NGC 7078, GCl 120 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. Messier 15 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 References