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Messier 18

Open Cluster M18 (NGC 6613), type 'd', in Sagittarius

Right Ascension 18 : 19.9 (h:m)
Declination -17 : 08 (deg:m)
Distance 4.9 (kly)
Visual Brightness 7.5 (mag)
Apparent Dimension 9.0 (arc min)

Discovered by Charles Messier in 1764.

Open cluster Messier 18 (M18, NGC 6613) is best observed in small telescopes, which show over a dozen of fairly bright stars (the Sky Catalog 2000 lists it with 20 members). It is about 0.2 degrees in diameter, thus appears loose and poor, its Trumpler type is given as II,3,p,n by all sources (where the "n" assigns to it some nebulosity). Its distance is about 4,900 light years, according to Kenneth Glyn Jones and Burnham, but the sources disagree: Mallas gives 6,000, the Sky Catalog 2000 has 3,900 light years. Adopting our value of 4,900 light years, its linear diameter should be about 17 light years.

As the hottest stars in M18 are of spectral type B3, this cluster is quite young; its age is estimated at 32 million years. As seen in the color image in our collection of more images of M18, this cluster contains bright blue as well as bright yellow or orange stars.

M18 is situated between the Omega Nebula M17 and the star cloud M24. This region around M17, M18 and M24 was photographed e.g. with the UK Schmidt Telescope.

Open cluster M18 is one of the original discoveries of Charles Messier, who cataloged it on June 3, 1764.

  • Historical Observations and Descriptions of M18
  • More images of M18
  • Amateur images of M18
  • Images of the M16, M17, and M18 region
  • Images of the M17, M18, and M24 region

  • WEBDA cluster page for M18
  • SIMBAD Data of M18
  • NED Data of M18
  • Publications on M18 (NASA ADS)
  • Observing Reports for M18 (IAAC Netastrocatalog)
  • NGC Online data for M18

    Hartmut Frommert
    Christine Kronberg

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    Last Modification: August 21, 2007