M103

The astronomical object number 103 of the Catalog Messier (noted M103 , or NGC 581 ) is a open Amas located in the Constellation of Cassiopée. He was discovered by Pierre Méchain in 1781, and belonged to the last objects includes by Charles Messier in his catalog of diffuse object, before he on the occasion to observe it besides itself.

This cluster is relatively not very dense and sparse, from where its classification of the type D , and it contains approximately 40 proven members. M103 is located roughly at 8 500 light-years of the Solar system, of which it approaches at the speed of 37 km/sec. Its apparent diameter of 6 minutes of arc corresponds, taking into account the distance, with approximately 15 light-years a real diameter.

The two most brilliant members of this cluster, of Magnitude connect +10,5, are a standard Supergéante of B5Ib and a Géante of the type B2III. The big number of stars belonging to the principal Séquence indicates a rather young age of 22 million years for the cluster.

Visually, the appearance of M103 is dominated by a very brilliant star in the foreground, quite visible over the images. It is acted in fact of a star doubles, but which does not form part of the cluster.

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