Messier 103

Messier 103 (also known as NGC 581 ) is a 7.4 like bright cluster with an angular extent of 6 ' in the constellation Cassiopeia. As seen from Earth, the heap is located in the Milky Way band, determining its distance with some uncertainty is associated; the distance of M 103 is estimated to be about 8,500 light-years. Its expansion is thus about 15 light-years. The radial relative velocity of M 103 to our solar system is about -40 km / s The age of M 103 is estimated according to recent calculations on approximately 25 million years. The star cluster was discovered in 1781 by Pierre -François- André Méchain. The brightest and most recognizable star in the range of M 103 is Struve 131 (HD 9311, SAO 11822 ), a multiple star with a 7.3 mag and a 10.5 like bright component. However, it is a foreground star, not belonging to the cluster M 103. The brightest actually belonging to M 103 Stars reach an apparent magnitude of 10.5 mag.

Messier 103 was the last object in the original published by Messier in three parts Messier catalog.