Wikipedia

NGC 188

NGC 188
Deep exposure of Polaris, integrated flux nebulae, and NGC 188
Observation data (J2000 epoch)
Right ascension00h 48m 26s[1]
Declination+85° 15.3′[1]
Distance6,000 ly (1.85 kpc[2])
Apparent magnitude (V)10.0[3]
Absolute magnitude (V)Unknown
Apparent dimensions (V)15′
Physical characteristics
Radius11.8 ly
Estimated age6.41 ± 0.33 Gyr[2]
One of the oldest known open clusters
Other designationsCaldwell 1, Cr 6, Mel 2[1]
Associations
ConstellationCepheus
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 or the Polarissima Cluster[4]) 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.[2]

NGC 188 is very close to the North Celestial Pole, under five degrees away, and in the constellation of Cepheus at an estimated 6,000 light-years' distance, this puts it slightly above the Milky Way's disc and further from the center of the galaxy than the Sun.

References

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  1. ^ a b c "NGC 188". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2006-12-08.
  2. ^ a b c Yakut, Kadri; Kalomeni, Belinda; Rappaport, Saul (2025). "A novel approach to determining the age of stellar clusters: Application to NGC 188". Monthly Notices of the Royal Astronomical Society. 542 (3): 1817–1826. arXiv:2508.09255. Bibcode:2025MNRAS.542.1817Y. doi:10.1093/mnras/staf1332.
  3. ^ Clark, R. N. (1990). Visual Astronomy of the Deep Sky. Cambridge University Press. p. 287. Bibcode:1990vads.book.....C. ISBN 978-0-521-36155-2.
  4. ^ Stoyan, Ronald; Schurig, Stephan (2014). interstellarum Deep Sky Atlas. Erlangen: Cambridge University Press; Oculum-Verlag GmbH. ISBN 978-1-107-50338-0. OCLC 920437579.
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