Exploring the birth and death of black holes and other creatures

Astronomers and physicists of diverse interest are teaming up to study enigmatic cosmic phenomena, such as the life cycle of black holes. A “disruptive innovation” is about to emerge during the next decade: Advanced gravitational-wave observatories. The emergence of gravitational-wave physics as a viable observational channel is expected to improve our understanding of the Universe in unprecedented and plausibly unexpected ways, and to enhance the capabilities of the astrophysics community. Detecting cosmic counterparts to gravitational-wave events would revolutionize our understanding of violent astrophysical processes, such as the birth and death of black holes and neutron stars. Although the vanguard of joint observational work with electromagnetic observatories has already rewarded us with a glimpse of the power of gravitational-wave astronomy, the most interesting science is yet to come. Many sources of gravitational-waves are expected to be observable through a broad set of messengers, including γ-rays, X-rays, optical, radio, and neutrino emission. Multimessenger investigations may be crucial for the first detection of gravitational-waves, and could provide the broadest scientific impact afterwards. This paper outlines some exciting aspects of transient multimessenger astronomy with gravitational-waves and highlights open questions that might be resolvable by Advanced or third generation gravitational-wave detector networks. In addition, we will use examples from current research to illustrate that the toolkit of fundamental research can enrich other fields, and that synergistic science can expand horizons here on Earth.