Indian Astronomers and Cutting-Edge Telescope Unleash the Enigmatic Symphony of Gravitational Waves

Indian Astronomers and the Symphony of Gravitational Waves: A Groundbreaking Discovery

In a monumental scientific achievement, an international team of astronomers, including researchers from seven prestigious Indian institutes, has captured the ethereal "hum" of gravitational waves resonating throughout the cosmos. This awe-inspiring phenomenon, long theorized by the brilliant mind of Albert Einstein, marks a pivotal milestone in our understanding of the universe.

At the forefront of this remarkable feat is India's upgraded Giant Metrewave Radio Telescope (uGMRT), standing proudly near Pune. Among the world's most sensitive radio telescopes, the uGMRT played a crucial role in unraveling the enduring hum of gravitational waves. These waves are believed to originate from the cosmic merger of supermassive black holes in the early stages of our universe, shortly after the cataclysmic Big Bang. With this groundbreaking discovery, scientists are poised to delve deeper into the mysteries surrounding the nature of these merging supermassive black holes and the forces that bind them together.

Published in a series of papers in The Astrophysical Journal Letters, these groundbreaking findings emerge from 15 years of meticulous observations conducted by the North American Nanohertz Observatory for Gravitational Waves (NANOGrav), which comprises over 190 scientists. The Indian Pulsar Timing Array (InPTA), leveraging the uGMRT, made vital contributions to this collective effort. The Indian telescope played a pivotal role in capturing and refining the gravitational wave signals, enhancing their accuracy and corroborating the celestial hum detected by their European counterparts.

The first pulsar timing array experiment commenced in 2002, with InPTA joining the endeavor in 2016. The InPTA initiative brings together researchers from esteemed institutions such as NCRA (Pune), TIFR (Mumbai), IIT (Roorkee), IISER (Bhopal), IIT (Hyderabad), IMSc (Chennai), RRI (Bengaluru), and collaborating colleagues from Kumamoto University, Japan.

While Albert Einstein initially proposed the existence of gravitational waves in 1916, it took nearly a century for their direct detection. In 2016, the National Science Foundation-funded LIGO observatory made history by detecting gravitational waves emanating from a distant collision of black holes. However, the waves detected by LIGO were of significantly higher frequency compared to those detected by NANOGrav.

Bhal Chandra Joshi from NCRA-TIFR, Pune, the visionary behind the InPTA collaboration, explains, "According to Einstein's theory, gravitational waves alter the arrival times of radio flashes emitted by pulsars, which serve as cosmic clocks. Until now, the discovery of these alterations eluded us due to their infinitesimal nature. Astronomers require sensitive telescopes like the upgraded GMRT and a network of radio pulsars to discern these subtle changes amidst other disturbances. The gradual variation of these signals necessitates decades of meticulous exploration to uncover these elusive nano-hertz gravitational waves."

Mayuresh Surnis, an assistant professor at the Indian Institute of Science Education and Research, provides further insights, stating, "If we were to convert these gravitational waves into sound, the background we detect could be likened to a hum. This background hum results from the overlapping waves generated by countless supermassive black hole binaries. As we continue analyzing the data, we will gain a deeper understanding of the specific types of black holes involved. While LIGO focuses on higher-frequency gravitational waves, our aim is to explore the entire spectrum of these extraordinary cosmic vibrations."

Yashwant Gupta, the center director at the National Centre for Radio Astrophysics (NCRA), Pune, responsible for operating the uGMRT, expresses his delight, stating, "Witnessing our uGMRT data being

 utilized for ongoing international efforts in gravitational wave astronomy is truly fantastic. The European PTA, in collaboration with our Indo-Japanese colleagues from InPTA, has unveiled comprehensive results derived from 25 years of pulsar data collected using six of the world's most prominent radio telescopes. This includes over three years of exquisitely sensitive data obtained through the unique low-frequency range and the remarkable versatility of India's largest radio telescope—the uGMRT."

Gupta further elaborates, "The signal we aim to extract from pulsars, these remnants of celestial stardom, is incredibly faint. As it traverses the galaxy, this signal becomes distorted by the intervening medium. To rectify this distortion, a low-frequency telescope like the GMRT becomes indispensable. Once the signal is cleansed, its accuracy improves, facilitating the detection of low-frequency gravitational waves responsible for this cosmic symphony."

To summarize the discovery:

- Gravitational waves emanate from the merger of supermassive black holes within galaxies.

- The convergence of these waves creates a celestial hum known as the stochastic gravitational wave background.

- Pulsars, rapidly rotating dead stars emitting radio beams, serve as precise cosmic clocks in a Pulsar Timing Array.

- Gravitational waves interact with pulsars, altering the arrival time of radio pulses on Earth, enabling their detection.

- Future research endeavors seek to deepen our understanding of the current signals, enabling the detection of individual merging binaries within galactic cores. Such breakthroughs will enable us to determine distances to these mergers and predict the universe's expansion rate during its early epochs.

The scientific community eagerly anticipates unraveling further mysteries concealed within the enigmatic vibrations of the cosmos, aided by the relentless pursuit of knowledge by Indian astronomers and the remarkable capabilities of the uGMRT.