A team of scientists from India, Japan, and Europe, including researchers from the Indian Institute of Technology, Roorkee (IIT-R), has successfully detected evidence of gravitational waves in the universe. The team employed advanced techniques, monitoring data from pulsars using six of the world’s most sensitive radio telescopes, including India’s largest telescope, uGMRT. This remarkable discovery, published in two seminal papers in the Astronomy and Astrophysics journal, confirms Albert Einstein’s theory of gravitational waves and sheds new light on the dynamics of the cosmos.
Pulsars, known as cosmic clocks, emit regular radio beams that are observed as flashes on Earth. Albert Einstein theorized that gravitational waves would affect the arrival times of these radio waves, altering the measured ticks of cosmic clocks. By carefully monitoring the irregular arrival times of pulsar signals using sensitive telescopes, astronomers deduced the presence of gravitational waves permeating the universe. These waves, characterized as nano-hertz gravitational waves, were found to originate from various sources, including pairs of supermassive black holes with masses millions of times greater than that of our Sun.
The National Centre for Radio Astrophysics (NCRA) in Pune, India, operates the uGMRT (giant meter wave radio telescope), which was crucial in this significant discovery. The team used uGMRT alongside other cutting-edge radio telescopes to detect and analyze the ripples in space-time caused by gravitational waves. The relentless cacophony of these waves, generated by numerous supermassive black hole pairs, contributes to the hum that pervades our universe.
Professor Arumugam from IIT Roorkee expressed his gratitude for the collective effort of numerous scientists, including early career researchers and undergraduate students, stating, “I am very grateful that IIT Roorkee has been able to constantly contribute in various ways in achieving these results.”
Albert Einstein first proposed the existence of gravitational waves in 1916 as an extension of his revolutionary theory of general relativity. Until 2016, scientists had relied on indirect evidence to support the existence of these waves. However, direct evidence became available with the successful detection of gravitational waves by the Laser Interferometer Gravitational-Wave Observatory (LIGO) in 2016. The recent research, which heavily relied on pulsar observations, further confirms Einstein’s theory by providing compelling evidence of low-frequency gravitational waves.
The detected gravitational waves, operating at low frequencies, contribute to a cosmic background hum that fills the universe. The study suggests that space is permeated by these waves, which oscillate over extended periods. The primary sources of these waves are believed to be pairs of supermassive black holes spiraling and merging together. Jeff Hazboun, an astrophysicist from Oregon State University and lead author of one of the papers published in the Astrophysical Journal Letters, explained, “As these waves travel through space, they physically stretch and compress the fabric of space-time itself.”
The discovery of gravitational waves in this new frequency range, significantly smaller than those previously detected by LIGO, opens up exciting possibilities for further understanding the dynamics of our cosmic neighborhood. While the most straightforward explanation involves pairs of supermassive black holes orbiting each other, alternative explanations may reveal intriguing new physics related to the early stages of the universe, potentially shedding light on the Big Bang and its aftermath.
