View from India: LIGO success heralds new era of Indian astronomy
On June 1 2017, the Laser Interferometer Gravitational-wave Observatory (LIGO) created history, when the LIGO Scientific Collaboration and Virgo Collaboration announced the detection of a gravitational wave signal from the coalescence of two stellar-mass black holes.
LIGO’s detection has been reported from the merger of two massive black holes that happened three billion light years away on January 4, 2017. Following the two detections during its first observing run in 2015-16, this is the third binary black hole coalescence that Advanced LIGO has detected.
The new detection occurred during the ongoing second observing run of the Advanced LIGO detectors in the USA, which began on November 30, 2016. The first direct observation of gravitational waves was made in September 2015 during the first observing run. A second detection was made in December 2015. The third detection, made on January 4, 2017, is described in a new paper accepted for publication in the journal Physical Review Letters.
View From India previously reported the detection of gravitational waves in February 2016. It also reported news about the direct observation of gravitational waves in September 2015.
The reason for reporting LIGO’s feat from time to time is because it has a strong connection with India. To be specific, 67 scientists from 13 Indian institutions are part of the LIGO Scientific Collaboration, under the umbrella of the Indian Initiative in Gravitational-Wave Observations (IndIGO). Some of the work related to data analysis has been carried out using the high-performance computing facilities at IUCAA Pune and International Centre for Theoretical Sciences (ICTS), a centre of Tata Institute of Fundamental Research (TIFR) in Bangalore.
“One of the most interesting predictions of Einstein’s theory of general relativity is the existence of gravitational waves. They are propagating changes in the geometry of spacetime - ripples in the fabric of space-time that carry energy and angular momentum away from the source. When gravitational waves pass through an object, they create a time-varying tidal force. These space-time strains can be measured by Michelson interferometers,” explained Abhirup Ghosh, a graduate student at ICTS and also working in the Astrophyiscal Relativity Group, as well as on the LIGO Scientific Collaboration. To mark the occasion, ICTS organised a special seminar by Ghosh.
“With the third definite detection of gravitational waves from a coalescing black hole binary, we have discovered a new class of astrophysical sources to test Einstein's theory of general relativity in extreme conditions,” said Bala Iyer, a Simons visiting professor at ICTS and the principal investigator of the Indian team in LIGO.
The ICTS group played a key role in developing and implementing an analysis that was used to test the consistency of the observed signals with general relativity. By combining results from multiple LIGO events, more precise constraints on deviations from the predictions of Einstein’s theory were obtained.
“What has opened up is a new precision laboratory. By combining results from the large number of events that LIGO will observe in near future, we will be able to perform stringent tests of Einstein’s theory,” explained Parameswaran Ajith, the principal investigator of the nine-member ICTS team in LIGO.
The team also contributed to the estimation of the mass and spin of the remnant black hole produced by the merger. By studying the masses and other properties of such binaries, future observations will tell us how exactly they are formed in nature. These Indian scientists and researchers along with a global consortium of scientists have contributed towards these detections.
Already the planned LIGO-India observatory that received in-principle approval from the Union cabinet in February 2016 has made rapid progress towards the plan to join these exciting scientific observations in 2024. Aundh in Hingoli district in Maharashtra will house the LIGO observatory. This is the third observatory: the first two are in the US, in Hanford, Washington, and in Livingston, Louisiana.
Thinking ahead, by 2024, when the LIGO-India observatory will be up and operational, it’s expected to unfold opportunities in cutting-edge technology. Make in India, a vision promoted by the present Union Government, should become the basis of many forthcoming initiatives envisioned by scientists, researchers, entrepreneurs and technocrats. Small-scale projects on squeezed light or a squeezed state of light needs to be encouraged because the properties of squeezed light can be used for ensuring better precision outcomes of gravitational wave detectors.
The fact that an advanced LIGO observatory is located outside US should attract foreign investors into India, especially those looking for scientific-astronomic observations. The premier higher educational institutes like the IITs, IIMs and IISc should open out multi-disciplinary studies and create a community of young professionals, ready to take on international collaborations on studies related to astronomy and gravitational wave detectors.