NGC 436, Open Star Cluster
The open star cluster NGC 436 is located at a distance of nearly 10,000 light-years in the constellation Cassiopeia and was found by F.W. Herschel in
November 1787.
Due to its proximity to the galactic plane, the light of the stars is slightly reddened and attenuated by upstream dust clouds. The color excess has a
value of E(B-V) = 0.555. So the light is attenuated by almost two magnitudes. The brightest stars of the cluster reach an apparent magnitude of
11.2mag, which corresponds to an absolute magnitude of -3.0mag or nearly 1,400 solar luminosities.
The angular extent of the cluster is given as 5'. From this a true diameter of 14 light-years can be calculated. For a star cluster this is quite a lot. The
age of NGC 436 was determined to 85 million years.
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In my 20" f/3 telescope NGC 436 offers a beautiful view at 270x. It is not particularly concentrated, but still stands out nicely from the surrounding
star field. There are about 50-55 individual stars with varying magnitudes visible. Especially striking is a triple chain of brighter stars near the center.
There is also a closer double star. In the eyepiece the cluster appears irregularly shaped - ring-shaped with outgoing star chains and a star-empty area
near the center. If you look closely, you can also find a brighter, yellowish-orange star in the southern part of NGC 436.
Because of its proximity to the well known owl cluster NGC 457 NGC 436 is a shadowy object - but wrongly. A visit is worthwhile in any case.
