Galaxy Formation Milky Way Galaxy Clusters Supermassive Black Holes Galaxy Mergers Quasars Spiral Galaxies Early Universe Kardashev Scale Dark Matter Structure Formation Cosmic Structures X-ray Astronomy Star Formation Satellite Galaxies Supernovae Galaxy Mapping Formation of Galaxies Intergalactic Medium Abell 370 Active Galaxies Black Holes Coma Cluster Galaxy NGC 6505 Nearby Galaxies NGC 6505 Galaxy NGC 6506 Blazars Galaxy Distribution Universe Structure Cosmic Sources Cosmic Evolution Gravitational Lensing Cosmic Mapping Galaxy Collisions Measurement Techniques Distance Measurement Advanced Civilizations Distant Galaxies Intergalactic Research Communication Signals