NGC 6866 - Open Cluster
NGC 6866 is an open star cluster in the constellation Cygnus that is best observed during the summer months. It was discovered in July 1783 by
Caroline Herschel. The cluster has an apparent diameter of 7' and a total brightness of 7.3mag. It can therefore be easily observed even in smaller
telescopes.
The true diameter of NGC 6866 is calculated to be 9 light-years. It contains around 80 stars, the brightest of which have an apparent magnitude
of 10.6mag. Using the known distance of 4,490 light-years, this results in an absolute magnitude of M= -0.1mag, which corresponds to the luminosity
of 100 suns. The total luminosity of NGC 6866 can be determined as 2,000 suns.
The metallicity of the stars is slightly higher than that of the Sun (100-130%). Different values are found for the age of the star cluster. The
observation of several giant stars (2023) yields a value of 430+-50 million years, while GAIA (also in 2023) has come up with an age of 780+-60
million years. In any case, the cluster is significantly younger than the sun and the solar system.
----------------------------------------------------------------------------------------------------------------------------------------------
The open star cluster NGC 6866 looks very nice in my 20” f/3 Dobsonian. :) It is slightly oval and the bright stars are evenly distributed. At a
magnification of 210x, around 40 individual stars can be seen, which are essentially equally bright. At the western edge of the cluster there is a
close double star. All in all a great object!
