Messier 11: The Wild Duck Cluster
Messier 11 is one of the most beautiful open star clusters in the northern sky. It is located in the constellation "Scutum", only a few degrees south of the celestial equator and rises 35°
above the horizon here in Germany. With a visual magnitude of 5.8mag and an apparent extent of 14' it is easily visible even with small binoculars.
Messier 11 is 6,100 light-years away from Earth and is one of the most star-rich and compact open star clusters in the Milky Way. An exact estimation of the total mass is difficult, so
the values vary between 4,000 and 11,000 solar masses. Up to 2,900 stars are said to belong to the cluster - about 800 of them are brighter than 16.5mag and thus theoretically visible
in a 50cm telescope. Many variable stars were found, but also some yellow and red giant stars. Single stars are gravitationally bound to the cluster up to a distance of 95 light years.
The brightest star of Messier 11 (HD 174512) is 8.5mag bright and belongs to spectral class B8. Using the distance an absolute magnitude of -2.9mag can be calculated. This corresponds
to a luminosity of 1,200 suns. So HD 174512 belongs to the group of white giant stars and is also part of a multiple star system. The other bright stars in Messier 11 typically have
absolute magnitudes of 0mag. If you now imagine living on a planet in the center of the wild duck cluster (maybe even in close proximity to the white giant star), the sky would be
littered with extremely many bright stars. HD 174512 would shine dazzling bright with -9mag in the sky and would be visible even during the day. But also many hundreds of other
stars would offer a spectacular sight on the firmament with magnitudes from -2mag to -6mag.
The age of Messier 11 is given with 220 to 300 million years, which makes it one of the younger of its kind.
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The view in my 50cm f/3 Dobson is simply stunning. Already at a low magnification of 120x the wild duck cluster is completely resolved. But the most beautiful view is at 210...270x.
The cluster appears quite large, but the whole field of view is filled with glittering stars. One can really dive into the flood of stars and is really carried away by the immense wealth of
stars. With indirect vision faint stars flash up everywhere between the many bright stars. Simply wonderful. To count the many stars seems almost hopeless. But in the drawing I took
the effort to count them and came up with nearly 240 single stars.
Especially exciting is the shape, which reminds me of a spiral, which rolls up from the inside to the outside counterclockwise. You can see dense areas with many bright stars, but also
star-poor areas or dark stripes. The overall shape seems to be more angular than round. Around the square central area something like a round halo of about 40 fainter stars can be seen.
Long story short: For me the Wild Duck Cluster is one of the most beautiful open star clusters on our firmament!
