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Globular Cluster M 10 (NGC 6254)

Date:7.5.1995 Time:01:37 UT Exposure:V: 5m, I: 5m
Field of View:22' x 21' Receiver: HoLiCam, 20482 CCD Filter:V, I
Instrument: 1m, f=3680mm Observatory: Hoher List Observer:T. Credner, S. Kohle

© Copyright by the observers

Astronomical Institutes of the University of Bonn

The bright globular cluster M 10 has a distance of 7.6 kpc in the direction of the constellation Ophiuchus. With its age of about 17 Gyr it belongs to a population of particular old globular star clusters.

From Colors to Astrophysics:

In the above color image you can easily distinguish between two major bright stellar populations: the blue and the brighter orange colored stars. The latter ones are red giants which exhausted their hydrogen in the cores and are now burning hydrogen in a shell. The blue stars are a step ahead in a quite stable phase of helium burning in their cores. The evolutionary transition between the red giants and the blue "horizontal branch" stars remains still unclear. This process must take a very short time, because no such stars in a transition phase could be observed.
Almost no normal hydrogen core burning stars are visible in the above image. They all evolved to the above described phases. Just the faintest and lowest mass stars are still burning hydrogen and appear very faint grey in the image.

The above image is a two color composit. Two exposures were taken with Johnson V and I filters and are represented with the two complementary colors blue and orange to show the data in a natural as possible appearing way with the right chromatic order.


  • Hurley, D.J.C., et al.:1989, AJ 98, 2124
  • Richtler, T., Galactic and Extragalactic Star Clusters, Lecture Notes, Bonn

    This image or former versions of it are already published in:

  • Astronomy Picture of the Day, March 12, 1999, NASA
  • The poster at the 1997 meeting of the Astronomische Gesellschaft in Innsbruck.
  • Tom Richtler: Kugelsternhaufen in Galaxien, Sterne und Weltraum [10/96]
  • the M 10 page of Hartmut Frommert