IC1805 Heart nebula in Cassiopeia is well known hydrogen cloud, very appreciated by astroimagers. This object is placed 6000 light years away. In its apparent center there is very young open star cluster – Melotte 15. Actually the cluster is about 50 light years closer to us than nebula. Average star age in this cluster is only 1.5 million years. Melotte 15 in IC1805 contains few bright stars OB about 50 times more massive than Sun, and pretty many small stars that are much less massive, than Sun. 

Three bright stars in the arc at right image part are spectral type O, which are the brightest and most massive stars known. They also live very short, typically 3 to 6 million years. Our Sun for comparison burns already 4.5 billion years, and it is in the middle of its way. 

I made image below with 10″ ACF telescope and QHY163M camera on EQ6 mount. It is 20 frames, 5 minutes each, aligned and stacked. Made under suburban sky, transparency was poor and seeing was good. Quite a lot of detail in hydrogen structures has been recorded due to decent seeing.

Melotte 15 cluster in the IC1805 Heart nebula
Melotte 15 cluster in the IC1805 Heart nebula

Large version here https://astrojolo.com/wp-content/uploads/2018/01/2018-01-15-Mel15H.jpg

Clear skies!