Open star clusters are the galaxy’s youngest stars. They are created from the collapse of giant molecular gas clouds, often forming large and very hot stars shinning brightly in the blue-white part of the spectrum.  As they are rapidly consuming their fuel, they are also short-lived.  By ending as a super nova, they create the heavier elements beyond carbon that exists all around us.

Below is open star cluster NGC 6633, estimated to be 660 million years old (our solar system is 4.6 billion years old). The cluster is of a decent size covering just about the size of a full Moon in the night sky.  The brighter and whitish stars stand out against older and further stars in the background.

Open Star Cluster NGC 6633

Younger star clusters such as the Pleiades (Messier 45) have yet to burn away their molecular gas clouds.  However there is no hint of glowing gas (nebula) with NGC 6633.

Skywatcher 80ED
Canon Rebel XTi
51x30sec (25.5 minutes) ISO 400