Pune, India – In a momentous scientific breakthrough that has set the global astronomical community abuzz, a formidable team of astronomers, including scientists from seven prestigious Indian institutes, has achieved a historic milestone by capturing the melodious resonance of low-frequency gravitational waves echoing across the vast expanse of the universe. This extraordinary achievement not only confirms the existence of gravitational waves, as originally predicted by the great Albert Einstein, but also opens up a new frontier of understanding in our quest to unravel the mysteries of the cosmos.
At the forefront of this groundbreaking discovery stands India’s upgraded Giant Metrewave Radio Telescope (uGMRT), located near the city of Pune. The uGMRT, recognized as one of the world’s six most sensitive radio telescopes, played a pivotal role in detecting and unraveling the persistent hum of gravitational waves. These waves are believed to have originated from the awe-inspiring merger of supermassive black holes in the early stages of the universe, shortly after the cataclysmic event known as the Big Bang. The implications of this revelation are profound, as scientists now have an unprecedented opportunity to delve deeper into the nature of these merging supermassive black holes and comprehend the cosmic forces that bring them together.
The remarkable findings, detailed in a series of meticulously crafted papers published in The Astrophysical Journal Letters, are the culmination of fifteen years of tireless observations by the North American Nanohertz Observatory for Gravitational Waves (NANOGrav). This international collaboration, which boasts over 190 dedicated scientists, includes the esteemed Indian Pulsar Timing Array (InPTA), utilizing the exceptional capabilities of the uGMRT. The Indian telescope played a pivotal role in collecting, refining, and enhancing the gravitational wave signals, enabling the corroborative confirmation of the resonant hum of the universe, as detected by their esteemed European counterparts, reports the Times of India.
The inception of the pulsar timing array experiment dates back to 2002, with the active participation of the InPTA commencing in 2016. This ambitious endeavor unites researchers from distinguished Indian institutions such as the National Centre for Radio Astrophysics (NCRA) in Pune, the Tata Institute of Fundamental Research (TIFR) in Mumbai, the Indian Institute of Technology (IIT) in Roorkee and Hyderabad, the Indian Institute of Science Education and Research (IISER) in Bhopal, the Institute of Mathematical Sciences (IMSc) in Chennai, and the Raman Research Institute (RRI) in Bengaluru. Collaborating with their counterparts from Kumamoto University, Japan, this collective scientific effort exemplifies the power of international collaboration in the pursuit of scientific knowledge.
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While the theoretical existence of gravitational waves was first postulated by Einstein in 1916, it took nearly a century before they were directly detected. In 2016, the groundbreaking Laser Interferometer Gravitational-Wave Observatory (LIGO), funded by the National Science Foundation, successfully recorded gravitational waves emanating from the collision of distant black holes. However, the frequency of gravitational waves detected by LIGO was significantly higher than those registered by NANOGrav.
Bhal Chandra Joshi, a distinguished scientist from the National Centre for Radio Astrophysics (NCRA-TIFR) in Pune and the visionary founder of the InPTA collaboration, emphasized the revolutionary nature of this discovery. According to Einstein’s theory, gravitational waves subtly alter the arrival times of radio flashes emitted by pulsars, often referred to as our cosmic clocks. Until now, the confirmation of this phenomenon had eluded scientists due to the minuscule nature of these changes. The elusive nano-hertz gravitational waves necessitate the use of sensitive telescopes like the upgraded GMRT and a meticulous collection of radio pulsars to discern these minute fluctuations from other environmental disturbances. The gradual evolution of this cosmic symphony demands decades of observation to unearth these elusive waves and unlock the secrets they hold.
Delving into the intricacies of the detection process, Mayuresh Surnis, an esteemed assistant professor at the Indian Institute of Science Education and Research in Bhopal, shed light on the profound implications of this groundbreaking discovery. When the detected gravitational waves are translated into sound, the resulting background can be aptly described as a resonant hum. This harmonic background arises from the superimposition of gravitational waves emitted by myriad sources, most notably the binaries formed by supermassive black holes. Further analysis of the data promises to unveil the precise nature of these celestial phenomena, shedding light on the characteristics of the black holes involved in these grand cosmic mergers. While LIGO has successfully detected high-frequency gravitational waves, the concerted efforts of the international scientific community aim to comprehensively explore the entire spectrum of gravitational wave frequencies.
Yashwant Gupta, the esteemed director of the National Centre for Radio Astrophysics (NCRA) in Pune, responsible for the operation of the uGMRT, expressed his enthusiasm at witnessing the utilization of Indian telescope data in ongoing international endeavors dedicated to gravitational wave astronomy. The European Pulsar Timing Array, in collaboration with their esteemed Indo-Japanese counterparts from the InPTA, has meticulously documented the results obtained through the rigorous analysis of pulsar data collected over a remarkable span of 25 years, employing the capabilities of six of the world’s largest radio telescopes. Notably, this comprehensive study incorporates over three years of exceptionally sensitive data collected utilizing the unique low-frequency range and the unparalleled versatility of India’s largest radio telescope – the uGMRT.
Gupta further highlighted the challenges posed by the faintness of the signals extracted from pulsars, which are essentially remnants of deceased stars. As these signals traverse the vast galactic medium, they undergo distortions that necessitate the intervention of a low-frequency telescope such as the GMRT. The corrective measures applied to these signals not only enhance their accuracy but also enable the detection of the low-frequency gravitational waves responsible for their generation.
In summary, the unveiling of the resonance created by merging supermassive black holes across the cosmos has opened up new avenues for scientific exploration. By detecting the stochastic gravitational wave background and analyzing its intricate nuances, scientists aspire to unravel the nature of these cosmic marvels. Furthermore, the future holds the promise of detecting individual merging binaries at the core of galaxies, paving the way for precise measurements of cosmic distances and early epoch universe expansion rates.
The discovery of the humming gravitational waves represents a giant leap forward in our understanding of the universe, reaffirming the timeless brilliance of Albert Einstein’s theories while igniting a new era of astronomical discovery and exploration. As humanity ventures further into the cosmic abyss, armed with cutting-edge technology and unwavering curiosity, we draw closer to deciphering the grand cosmic symphony that resonates throughout the cosmos.
