Pune: GMRT in Pune first Indian institution to detect gravitational waves
Pune, June 30, 2023: In an unprecedented scientific breakthrough, the National Centre for Radio Astrophysics (NCRA) has announced the detection of nano-hertz gravitational waves by the Giant Metrewave Radio Telescope (GMRT) in Pune, India. The GMRT was one of six international telescopes integral to this groundbreaking discovery.
Gravitational waves, as theorized by Albert Einstein, were first confirmed eight years ago. This new finding arrives as two separate studies from the Indian Pulsar Timing Array (InPTA) and European Pulsar Timing Array (EPTA) reveal time anomalies in signals coming from pulsars.
These spinning neutron stars, termed as cosmic clocks, regularly emit radio signals and are of high scientific interest due to their potential to unveil universe secrets. Scientists use a collection of these ultra-stable pulsar clocks, scattered throughout the Milky Way, to establish an imaginary gravitational wave detector on a galactic scale.
The presence of gravitational waves impacts the detection of other signals in the universe, causing them to arrive early or with slight delays on Earth. These variations in arrival time, which are less than a millionth of a second, are triggered by nano-hertz signals described as a cosmic hum. Scientists attribute this hum to gravitational waves and signal anomalies from pulsars.
According to Bhal Chandra Joshi, senior NCRA scientist, these irregularities cause consistent effects on the resultant ultra-low-frequency gravitational waves.
The ultra-low-frequency, or nano-hertz gravitational waves, are believed to originate from colossal black holes many millions times the mass of the Sun. Such black holes are usually found in the cores of colliding galaxies, and the signals or waves emanating from them are known as nano-hertz gravitational waves.
Six of the world’s leading radio telescopes, including the GMRT, studied 25 pulsars over 15 years, along with analysis of GMRT data from over three years. Their conclusion was that the radio flashes from these pulsars were influenced by nano-hertz gravitational waves from massive black holes.
The InPTA team includes experts from various Indian research institutions along with NCRA scientists. Even though the Laser Interferometer Gravitational Observatory (LIGO) detected these waves over short periods, PTAs observed these signals at different frequencies.
Professor A Gopakumar from the Tata Institute of Fundamental Research, Mumbai, stated that the galactic-sized PTA was able to sense the continuous vibration of the gravitational wave background at nano-hertz frequencies.
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Joshi reiterated Einstein’s belief that gravitational waves alter the arrival times of radio flashes, thereby affecting our cosmic clocks. He added that detecting these minute changes requires sensitive telescopes like GMRT and a collection of radio pulsars. The GMRT’s high-quality data from low-frequency radio bandwidth, facilitated by the whiteband receiver systems, was instrumental in this discovery, added Yashwant Gupta, Centre Director at NCRA.
This international collaborative effort was applauded by Professor Michael Kramer, Director of the Max-Planck Institute, Germany, as scientifically rewarding and a model for future global International Pulsar Timing Array initiatives.
