MSV-2035 Astronomy Document - Inside Design - FINAL - FINAL

Astronomy & Astrophysics 36 coordination by the global observational astronomy community. In the last six years the LIGO-Virgo observatories have yielded nearly hundred confirmed detections of a variety of merger events involving black holes and neutron stars. Enormous amount of science has resulted from these observations in a short span of time.We learned that there is a large population of heavy black holes in the universe, intermediate mass (more than 100 times the mass of the sun) black holes were discovered; it was firmly established that good fraction of heavy metals like gold in the Universe was created in binary neutron star mergers; equation of state of nuclear matter in the neutron stars was constrained; we obtained an independent estimate of the expansion rate of the Universe which may help us in resolving the conflicting measurements obtained fromother astronomical observations, andmanymore. A massive effort is underway across the globe for building new detectors, upgrading the existing detectors and advancement of theoretical studies to promote rapid progress in the budding field of Gravitational Wave Astronomy, partly envisioning significant technological spin offs. Second generation detectors: The Advanced LIGO and Virgo detectors are being upgraded to the Advanced+ (A+) sensitivities. LIGO-India will also have the same configuration. The volume within which these can detect events of a given kind will be nearly ten times larger than the present detectors. The plans, site-selection and technology demonstration programmes for building next generation GW detectors are moving at a fast pace across the globe. There is an ongoing effort to design major upgrades of the present detectors, often referred to as LIGO-Voyager, which will use the existing sites, thus enormously cost-effective compared to the third generation detectors and highly relevant for LIGO- India. Third generation detectors: The international GW community is pushing two massive detectors to be built in the next two decades - the Einstein Telescope (ET) in Europe and Cosmic Explorer (CE) in the USA.According to the current plans, ETwill be an equilateral triangle shaped underground detector with 10-km arms and CE will be an L-shaped 40-km long detector on the ground. Clearly, these are gigantic detectors, demanding enormous resources. The respective scientific community and the funding agencies are seriously pursuing these efforts: a site selection campaign across Europe was conducted for ETand a three year funding for conducting a concept study for CE has been granted. Milli-Hertz detectors: Frequencies of black hole mergers reduce with as their masses increase. It is well known that the Universe is full of supermassive black holes, though their exact numbers, distribution of mass, distance and other properties are barely known. Ground based detectors may never be able to operate below 1Hz due to seismic noise. Space based detectors with million-kilometer arm lengths will be able to detect the mergers of supermassive black holes. Also, they will be able to observe the inspiral phase of the smaller compact stars and alert when such a merger will be detected by ground based GW& EM observatories. These missions are developing high power Lasers for space and “drag-free” environment in spacecrafts using micro-thrusters, which may have broader application. There are two major international missions aiming for launches in the 2030s, Laser Interferometer Space Antenna (LISA) by the European SpaceAgency andTianQin by China. Deci-Hertz detectors: The milli-Hertz and the ground-based detectors leave a gap in the deci-Hertz frequency window. A detector in this band, apart from providing early alerts for stellar mass binary • • • • MEGA SCIENCE VISION-2035