A proposal for the first-ever space-based observatory for studying gravitational waves just passed a vital feasibility review with flying colors. The mission is called LISA — the Laser Interferometer Space Antenna—And it cleared Phase A of its mission lifetime cycle, the process by which missions are dreamt up and then created.
Led by the European Space Agency in collaboration with NASA, LISA is made up of three spacecraft that will orbit the Sun in a triangular formation. Each ‘side’ in that triangle will be 1.5 million miles long. As an interferometer (like the ground-based LIGO), LISA will very precisely keep track of the distance between the three spacecraft. When a passing gravitational wave causes a distortion in spacetime, LISA will detect it as the distance between its spacecraft briefly changes. LISA will also be able to detect where in the sky the gravitational wave came from.
Gravitational waves, predicted to exist by Einstein, are produced by some of the most extreme astrophysical phenomena in the universe. When black holes and neutron stars — some of the densest, most massive objects out there — orbit one another or merge, they cause ripples in the fabric of spacetime.
Since LIGO made history by detecting gravitational waves in 2015, astrophysicists have become determined to see more of these ripples, but some are harder to observe than others. Mergers of different masses produce waves of different frequencies; small black hole mergers and explosive events like supernovae are detectable by observatories like LIGO, but supermassive black hole mergers emit frequencies that LIGO’s 2.5-mile-long arms are simply too short to detect. LISA’s 1.5-million-mile arms will be able to detect lower frequency events, like those clashes of giant black holes.