deutsch english español language

Open Cluster M 50 (NGC 2323)

Date:23./25.10.1995 (B&I/V) Time:2:25 UT (B,I), 2:50 UT (V) Exposure:B:42m, V:8m, I:4m
Field of View:20' x 15' Receiver: WWFPP, 20482 CCD Filter:B,V,I
Instrument: 1.23m Observatory: Calar Alto Observer:T. Credner, S. Kohle

© Copyright by the observers

Astronomical Institutes of the University of Bonn

From Colors to Astrophysics:

How this three color image can be interpreted in astrophysics.

The presence of the bright blue stars shows, that this Open Cluster has a young age, because this massive, hot and short living stars are still existing. On the other hand there are already some bright red stars, which seem to be evolved Red Giants (with the assumption, that they are really cluster members!). So a minimum age of the cluster is given.

Another interesting aspect of this image is, that all the faint stars appear red. Partly this is due to the general tendency of the main branch in the Color-Magnitude-Diagram, that means the faint stars are low mass objects, cool and red. But M 50 is positioned directly in the plane of our galaxy, so we expect most faint stars not to be cluster members. They just appear faint, because of their larger distances. And due to the color dependent extinction in the interstellar dust, that means the blue part of the spectrum is scattered out much more than the red part, they appear red. So this image also shows, that you can reach much deeper into the inner center of our galaxy in the infrared part of the spectrum.

This image is already published in:

  • Sterne und Weltraum [1/2000]
  • IBM Research Page, October 1997, about fractal theory and stellar mass functions (B. Elmegreen).
  • Astronomy Picture of the Day, January 28, 1997, NASA
  • Till Credners Diploma Thesis, 1996, University Bonn
  • the M50 page of Hartmut Frommert