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Open Cluster NGC 1245

Date:21./22.10.1995 (V&I/B) Time:22:30 UT (V,I), 22:55 UT (B) Exposure:B:85m, V:18m, I:5m
Field of View:20.1' x 18.0' 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

This three color composite is consisting of Johnson B, V, and I filter exposures, represented in blue, green, and red respectively. The composite is assembled with a special technique to preserve and present the original physical star colors.

The Open Star Cluster NGC 1245 has a distance of about 2.5 kpc in the direction of the constellation Perseus. Like in NGC 2194 most bright stars of the cluster show a slightly blue color. These are the "normal" hydrogen core burning stars with their hot surface temperature. But there are also a lot of bright orange stars. They are evolved, i.e. they already left the usual stage of hydrogen core burning and started hydrogen shell burning. Some might already burn helium in their cores. The orange color is due to their cooler surface temperature. The relative large number of these evolved stars is a hint for the old age of the cluster. Indeed NGC 1245 is with 109 years about ten times older than the cluster M 50, and so belongs like NGC 2194 to the unusual population of old or intermediate age Open Clusters in our Galaxy.
The two very bright blue stars are most probable foreground objects of the galactic field, i.e. they are no cluster members.

  • 1994A&A...289..397C, CARRARO, G.; PATAT, F., CCD BV photometry of the intermediate age open cluster NGC 1245
  • Open Cluster Data 5th Edition (Lynga 1987) at CDS Strasbourg.
  • SEDS infos