Pune-based radio telescope helps detect universe’s vibrations
The Pune-based Upgraded Giant Metrewave Radio Telescope (uGMRT) was among the world’s six large telescopes used to analyse pulsar data collected over 25 years
PUNE The results of monitoring pulsars – Nature’s best clocks – using six of the world’s most sensitive radio telescopes, including India’s largest telescope, the Upgraded Giant Metrewave Radio Telescope (uGMRT) located near Pune, provide a hint of evidence for the relentless vibrations of the fabric of the universe caused by ultra-low frequency gravitational waves. Such waves are said to originate from a large number of dancing, monster, black hole pairs, crores of times heavier than our Sun. The results published by a team of astronomers from India, Japan and Europe help open a new, Astro-physically rich window in the gravitational wave spectrum.
Professor Bhal Chandra Joshi of NCRA-TIFR Pune who founded the Indian Pulsar Timing Array (InPTA) collaboration during the last decade, said, “According to Einstein, gravitational waves change the arrival times of these radio flashes and thereby affect the measured ticks of our cosmic clocks. These changes are so tiny that astronomers need sensitive telescopes like the uGMRT and a collection of radio pulsars to separate these changes from other disturbances. The slow variation of this signal means it has taken decades to look for these elusive nano-hertz gravitational waves.”
“Such dancing, monster, black hole pairs, expected to lurk at the centre of colliding galaxies, create ripples in the fabric of our cosmos, and astronomers call them nano-hertz gravitational waves as their wavelengths can be many lakhs of crores of kilometres. The relentless cacophony of gravitational waves from a large number of supermassive black hole pairs creates a persistent humming of our universe. The team, consisting of members of the European Pulsar Timing Array (EPTA) and InPTA consortia, published their results in two papers in the ‘Astronomy and Astrophysics Journal’ and their results hint at the presence of such gravitational waves in their data set,” professor Joshi said.
Scientists of the EPTA and their Indo-Japanese counterparts from the InPTA have reported detailed results of analysing pulsar data collected over 25 years with six of the world’s largest radio telescopes namely, the 100-m Effelsberg Radio Telescope in Germany; the Lovell Telescope of the Jodrell Bank Observatory in the United Kingdom; the Nancay Radio Telescope in France; the Sardinia Radio Telescope in Italy; the Westerbork Synthesis Radio Telescope in the Netherlands; and the uGMRT.
Professor Yashwant Gupta, centre director, NCRA-TIFR which runs the uGMRT, said, “It is fantastic to see our unique uGMRT data being used for the ongoing international efforts on gravitational wave astronomy. Carrying out high precision timing of pulsars for such a purpose was one of the crucial science targets of the major upgrade of the GMRT that we carried out during 2013-2019, and I am extremely pleased to see it bearing fruit within the first few years. The wideband receiver systems that we designed and built for the upgraded GMRT are the ones that have enabled the high-quality data from the lower radio frequencies that the GMRT is contributing to the international collaboration.”
Professor A Gopakumar, TIFR Mumbai and chair of the InPTA consortium, said, “The results presented today mark the beginning of a new journey into the Universe to unveil some of its mysteries. More importantly, this is the first time that an Indian telescope’s data has been used for hunting gravitational waves. To detect these gravitational wave signals, astronomers in a ‘Pulsar Timing Array or PTA’ collaboration exploit many ultra-stable pulsar clocks, distributed across our Milky Way galaxy to create a ‘galactic-scale gravitational wave detector’. Measurements of the exact arrival times of the pulsars, which have been going on for decades, are being compared with each other to study the influence of gravitational waves.”
Professor Michael Kramer, director, Max-Planck Institut fur Radioastronomie, Bonn, Germany, who along with professor Joshi has been instrumental in the close collaboration between the European and Indian PTAs, said, “Our collaboration between colleagues across Europe, India and Japan not only shows that an international effort is successful and very rewarding scientifically, but we hope to also serve as a role model for the global IPTA efforts.”
Professor Shantanu Desai, IIT Hyderabad, said, “The results reported by the EPTA-InPTA collaboration are tantalisingly close to the discovery of nano-hertz gravitational waves and are the culmination of many years of efforts by many scientists, including early career researchers and undergraduate students. We are grateful to the NSM computing facilities at IIT Hyderabad and IIT Roorkee, along with the computing infrastructure of NCRA Pune and TIFR Mumbai which helped unveil these results.”
