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Gravitational Wave Astronomy on the ground and in space
Gravitational Wave Astronomy on the ground and in space
On 14 September 2015, scientists have observed ripples in the fabric of spacetime called gravitational waves for the first time, arriving at the earth from a cataclysmic event in the distant universe. This confirms a major prediction of Albert Einstein’s 1915 general theory of relativity and opens an unprecedented new window onto the cosmos. The observed event was the final merger of a binary black hole system. This is the beginning of a new era in astronomy.
Gravitational wave astronomy will open an entire new window on our Universe. Gravitational waves are produced by violent events in the distant universe, for example by the collision of two black holes or by the cores of supernova explosions. They are emitted by accelerating masses much in the same way as radio waves are produced by accelerating charges – for example, such as electrons in antennas. These ripples in the space-time fabric travel to Earth, bringing with them information about their violent origins and about the nature of gravity that cannot be obtained by other astronomical tools.
Gravitational Wave Observatories on the ground are now observing Gravitational Waves and new 3rd generation detectors detectors are already being planned. With the success of LISA Pathfinder we have also taken the first steps toward building a Gravitational-Wave Observatory in space.
Groups in the UK and Germany made essential contributions to the detection in the fields of material science, lasers and optics, laser interferometry, high-speed computing, data analysis and astrophysics. Scientists at GEO600 have pushed the available technologies to the limits: laser stabilization, absorption-free optics, control engineering, vibration damping and data acquisition and processing got new impulses. The suspension of the mirror on glass fibers is only one of the many groundbreaking developments of GEO600. Another specialty of GEO600 is the amplification of laser light and signal called "dual recycling": This technique allows a tuning of the detector to a certain frequency. GEO600 is also the first gravitational wave detector that uses squeezed laser light in order to improve sensitivity!
GEO600 is a ground-based interferometric gravitational wave detector located near Hannover, Germany. It is designed and operated by scientists from the Max Planck Institute for Gravitational Physics, along with partners in the United Kingdom and is funded by the Max Planck Society and the Science and Technology Facilities Council (STFC). GEO600 is part of a worldwide network of gravitational wave detectors. Two detectors have been constructed in the USA (LIGO), and one each in Italy (Virgo) and Japan (KAGRA). Scientists from GEO600 and LIGO collaborate within the LIGO Scientific Collaboration (LSC). GEO600 scientists together with the Laser Zentrum Hannover (LZH) built the special high-powered lasers for Advanced LIGO.
LISA Pathfinder, a mission led by the European Space Agency (ESA) with contributions from NASA, has successfully tested a key technology needed to build a space-based observatory for detecting gravitational waves. These tiny ripples in the fabric of space, predicted by Albert Einstein a century ago, were first seen last year by the ground-based Laser Interferometer Gravitational-Wave Observatory (LIGO). Scientists say the results are nothing short of astonishing. Non-gravitational forces on the cubes were reduced to levels far below the project's original requirements and approach the level of control needed for a full-scale observatory.
LISA will be the first observatory in space to explore the Gravitational Universe. It will gather revolutionary information about the dark universe.. The LISA mission consists of three spacecraft orbiting the Sun in a triangular configuration, connected by three arms of a laser interferometer. The three satellites, separated by a distance of million km, will form a high precision interferometer that senses gravitational waves by monitoring the changes in distance between free falling test masses inside the spacecraft. The laser interferometer has an arm length of 2.5 million km.
Launched in December 2015, LISA Pathfinder travelled to its operational orbit, 1.5 million km from earth towards the Sun, where it started its scientific mission on 1 March. Over the first two months of scientific operations, the LISA Pathfinder team has performed a number of experiments on the test masses to prove the feasibility of gravitational wave observation from space. These results are explained in this video with interviews of Paul McNamara, LISA Pathfinder Project scientist, ESA and two LISA Pathfinder Principal investigators : Rita DOLES, University of Trento and Martin Hewitson, University of Hannover.
LISA Pathfinder will pave the way for future missions by testing in flight the very concept of gravitational wave detection: it will put two test masses in a near-perfect gravitational free-fall and control and measure their motion with unprecedented accuracy. LISA Pathfinder will use the latest technology to minimise the extra forces on the test masses, and to take measurements. The inertial sensors, the laser metrology system, the drag-free control system and an ultra-precise micro-propulsion system make this a highly unusual mission. LISA Pathfinder is an ESA mission, which will also carries a NASA payload. Launched in December 2015, LISA Pathfinder travelled to its operational orbit, 1.5 million km from earth towards the Sun, where it started its scientific mission on 1 March.
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