LISA – Bringing the Gravitational Wave Revolution to Space

• Ira Thorpe (NASA Goddard Space Flight Center)

Gravitational Wave (GW) observatories are humanity’s newest tool for studying the universe. After decades of development efforts, terrestrial interferometers such as LIGO and Virgo are now routinely detecting ripples in the fabric of spacetime caused by distant astrophysical cataclysms such as the collision of black holes. Early results from these instruments have already provided answers to long-standing questions in astrophysics and, more importantly, introduced new questions of their own. However, even as instruments on the Earth continue to improve, there will be vast portions of the GW spectrum that will not be accessible due to their limited size and noise in the terrestrial environment. Space-based interferometers a million times larger than their terrestrial cousins will probe the milliHertz GW spectrum, home to a rich variety of astrophysical signals. In this talk, I will provide an overview of the Laser Interferometer Space Antenna (LISA), an international collaboration to develop the first space-based GW interferometer. I will describe the science applications, the mission concept, and key technologies behind what will be the largest scientific instrument ever constructed. I will also highlight the contributions of LISA Pathfinder, a European-led technology demonstration mission that validated several critical aspects of the LISA concept.

Infrared Interferometry of the Galactic Center Black Hole

• Frank Eisenhauer (Max Planck Institute for extraterrestrial Physics)

The Galactic Center harbors the nearest massive black hole. With a distance of only 8 kpc, it is the closest laboratory to study the astrophysical processes at work in these extreme objects, and to probe Einstein's general theory of relativity in the regime of strong gravity. Our presentation gives an overview of the GRAVITY infrared interferometry observations leading to the detection of the gravitational redshift and the Schwarzschild precession in the orbit of a star orbiting the black hole in a 16 yr orbit, and the observations of orbital motion of hot gas close to the innermost stable orbit. We further present the perspective for future measurements of the spin and quadrupole of the black hole by combining infrared interferometry and spectroscopy form extremely large telescopes, which will then also test the cosmic censorship and no hair theorem of black holes.

Gravitational waves in a new light

• Michèle Heurs (AEI Hannover)

Ultra-precisely stabilised lasers are the interferometric light sources at the heart of gravitational wave detectors. To achieve ever-higher detection rates for meaningful gravitational wave astronomy, ever-greater detection sensitivity is required. In this talk I will introduce the principle of interferometric gravitational wave detection, and highlight some of the advanced technologies employed in Advanced LIGO. Current-generation gravitational wave detectors are already limited by quantum noise of the laser light over wide ranges of their detection band. One sophisticated technique that is already routinely being employed to increase the quantum-limited sensitivity of gravitational wave detectors is the use of non-classical (fixed-quadrature squeezed) light. I will conclude my talk by showing some recent results, as well as options for quantum noise reduction in laser interferometry and the broader field of quantum optics.