Kronberger 31, Open Star Cluster
The star cluster "Kronberger 31" is located in the constellation "Vulpecula". At the moment, two different values of the distance are in use:
one is about 39,000 light-years from a study from 2006, a newer study from 2022, however, comes to a much smaller distance of 25,500
light-years.
The total mass of the Open Cluster was determined to be 8,300 solar masses. Using the apparent diameter of 1.1' the true size of "Kronberger
31" can be determined to about 10 light-years, but the stars are still gravitationally bound to the cluster up to a distance of 60 light-years.
Investigations have also shown that about 80% of the members are double stars.
The age of "Kronberger 31" is almost exactly 1 billion years, so it is quite old.
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In a 20" telescope a very faint roundish glow can be seen at a magnification of 270x. The cluster appears brighter than "Berkeley 56", which
was observed shortly before. The shape is roundish and the background appears slightly grainy, but without really showing single stars. The
OC is located in a group of bright stars, which looks quite nice.
