Galaxy Formation Milky Way Galaxy Mergers Supermassive Black Holes Galaxy Clusters Spiral Galaxies Advanced Civilizations Distant Galaxies Intergalactic Research Communication Signals Kardashev Scale Early Universe Structure Formation X-ray Astronomy Star Formation Satellite Galaxies Supernovae 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 Galaxy Collisions Gravitational Lensing Distance Measurement Measurement Techniques