Cluster + nebula

A young star cluster still embedded in the cloud of gas it formed from, which its stars make glow.

Stars are born in clusters inside clouds of gas. For a few million years the youngest, hottest stars light up the leftover gas as an emission nebula, so we see the cluster and its nebula together. The Eagle Nebula (M 16) and the Orion Nebula with its Trapezium are the best known.