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NGC 6341
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Messier 92 (also known as M92, GCL 59 or NGC 6341) is a magnitude +6.3 globular cluster located 26,700 light-years away in the constellation Hercules.
The cluster is visible to the naked eye under very good conditions. In small telescopes (four to eight-inch), the cluster can be resolved into individual stars.
M92 can be found exactly 6.3 north of the third-magnitude star Pi Herculis.

The cluster was discovered by German astronomer Johann Elert Bode, possibly with a small refractor at the Berlin Observatory, on the 27th December 1777, then published in the "Astronomisches Jahrbuch" during 1779. The cluster was independently rediscovered by Charles Messier in Bath, England, on March 18, 1781 and added as the 92nd entry in his catalogue. M92 was classified as a star cluster by William Herschel in 1783.

m92


Right ascension 17h 17m 07.39s, Declination +43 08' 09.4"



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RE: Messier 92
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Title: On the density profile of the globular cluster M92
Authors: A. Di Cecco, A. Zocchi, A. L. Varri, M. Monelli, G. Bertin, G. Bono, P. B. Stetson, M. Nonino, R. Buonanno, I. Ferraro, G. Iannicola, A. Kunder, A. R. Walker

We present new number density and surface brightness profiles for the globular cluster M92 (NGC 6341). These profiles are calculated from optical images collected with the CCD mosaic camera MegaCam at the Canada-France-Hawaii-Telescope and with the Advanced Camera for Surveys on the Hubble Space Telescope. The ground-based data were supplemented with the Sloan Digital Sky Survey photometric catalogue. Special care was taken to discriminate candidate cluster stars from field stars and to subtract the background contamination from both profiles. By examining the contour levels of the number density, we found that the stellar distribution becomes clumpy at radial distances larger than about 13 arcminutes, and there is no preferred orientation of contours in space. We performed detailed fits of King and Wilson models to the observed profiles. The best-fit models underestimate the number density inside the core radius. Wilson models better represent the observations, in particular in the outermost cluster regions: the good global agreement of these models with the observations suggests that there is no need to introduce an extra-tidal halo to explain the radial distribution of stars at large radial distances. The best-fit models for the number density and the surface brightness profiles are different, even though they are based on the same observations. Additional tests support the evidence that this fact reflects the difference in the radial distribution of the stellar tracers that determine the observed profiles (main sequence stars for the number density, bright evolved stars for the surface brightness).

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Messier 92 (also known as M92 or NGC 6341) is a globular cluster of stars in the northern constellation of Hercules.
It is visible to the naked eye under very good conditions.

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