... The Hercules Cluster of Galaxies . ... Also known as Abell 2151, this cluster is loaded with gas and dust rich, star-forming spiral galaxies but has relatively few elliptical galaxies, which lack gas and dust and the associated newborn stars. The Iris Nebula in a Field of Dust . ... What flowers in this field of dark star dust? ... The striking blue color of the Iris Nebula is created by light from the bright star SAO 19158 reflecting off of a dense patch of normally dark dust. ...