NGC 188

Coordinates: Sky map 00h 48m 26s, +85° 15′ 18″
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NGC 188
NGC 188
Observation data (J2000 epoch)
Right ascension00h 48m 26s[1]
Declination+85° 15.3′[1]
Distance5,400 ly[2] (1.66 kpc)
Apparent magnitude (V)10.0[3]
Apparent dimensions (V)15
Physical characteristics
Radius11.8 ly
One of the oldest known open clusters
Other designationsCaldwell 1, Cr 6, Mel 2[1]
See also: Open cluster, List of open clusters
HR diagram showing the main sequence turnoff of NGC 188 and M 67, indicating their relatively high ages

NGC 188 (also known as Caldwell 1) is an open cluster in the constellation Cepheus. It was discovered by John Herschel in 1825. Unlike most open clusters that drift apart after a few million years because of the gravitational interaction of our Milky Way galaxy, NGC 188 lies far above the plane of the galaxy and is one of the most ancient of open clusters known, at approximately 6.8 billion years old.[4]

NGC 188 is very close to the North Celestial Pole, under five degrees away, and in the constellation of Cepheus at an estimated 5,000 light-years' distance, this puts it slightly above the Milky Way's disc and further from the center of the galaxy than the Sun.


  1. ^ a b c "NGC 188". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2006-12-08.
  2. ^ Bonatto, C.; Bica, E.; Santos, J. F. C. Jr. (2005). "Spatial dependence of 2MASS luminosity and mass functions in the old open cluster NGC 188". Astronomy and Astrophysics. 433 (3): 917–929. arXiv:astro-ph/0502453. Bibcode:2005A&A...433..917B. doi:10.1051/0004-6361:20041113.
  3. ^ Clark, R. N. (1990). Visual Astronomy of the Deep Sky. Cambridge University Press. p. 287. ISBN 978-0-521-36155-2.
  4. ^ VandenBerg, D. A.; Stetson, P. B. (2004). "On the Old Open Clusters M67 and NGC 188: Convective Core Overshooting, Color‐Temperature Relations, Distances, and Ages". Publications of the Astronomical Society of the Pacific. 116 (825): 997–1011. Bibcode:2004PASP..116..997V. doi:10.1086/426340.

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