Supermassive black holes have emerged over the last decade as a cornerstone of astronomy, astrophysics, and public engagement with science, though their foundational importance was established as early as the 1960s.

This book serves as an introduction to the evolving frontiers of modern astronomy and cosmology, with supermassive black holes and their binaries as the unifying theme. It examines the theoretical and observational investigations that have revealed the pivotal role of such binaries in shaping cosmic evolution. Woven throughout is the social and historical landscape that made these discoveries possible, along with the compelling human stories of the researchers behind them.

 The book further offers a window into recent advances in gravitational wave astronomy and explores the far-reaching implications of detecting mergers between supermassive black holes.

Mauri Valtonen has worked on supermassive binary black hole problems since his graduation from the University of Cambridge in 1975. His affiliations include the Institute of Physics in Helsinki, the National Radio Astronomy Observatory in the USA, the University of Alabama, Metsähovi Radio Observatory, and the longest as professor of Astronomy at the University of Turku, Finland.

Achamveedu Gopakumar is a Professor at the Tata Institute of Fundamental Research, Mumbai, India. His research centers on gravitational waves and the general relativistic aspects of black hole binaries, a field in which he has collaborated closely with Mauri Valtonen since 2008. Beyond his core research, he is a founding member of the Indian Pulsar Timing Array (InPTA) and  serves on the International Advisory and Evaluation Committee of the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC), Beijing, China.