Listening to the Universe with New Gravitational Wave Observatories
B. Sathyaprakash is a lead author on the cover story of the May 2021 issue of Nature Physics Reviews on the future of gravitational-wave astronomy. As Abhay Ashtekar explained, “Gravitational-wave observations of binary black-hole and neutron-star mergers by LIGO and Virgo have opened a completely new window on the Universe. The gravitational-wave spectrum, extending from attohertz to kilohertz frequencies, provides a fertile ground for exploring many fundamental questions in physics and astronomy.” Pulsar timing arrays probe the nanohertz to microhertz frequency band to detect gravitational-wave remnants from past mergers of supermassive black holes. The space-based Laser Interferometer Space Antenna will target gravitational-wave sources from microhertz up to hundreds of millihertz and trace the evolution of black holes from the early Universe through the peak of the star formation era. Einstein Telescope and Cosmic Explorer, two future ground-based observatories now under development for the 2030s, are pursuing new technologies to achieve a tenfold increase in sensitivity to study compact object evolution to the beginning of the star formation era. As Sathyaprakash put it, “Gravitational-wave observations provide a new tool for observing the Universe, and future observatories are guaranteed to make discoveries that could transform our understanding of many of the current problems in physics and Astronomy.”