Astronomers detect ultra-low freq waves using pulsar and radio telescopes

This is the first time data from an Indian telescope has been used to hunt for gravitational waves

An international team of astronomers with scientists from India, Japan, and Europe, have found evidence of the existence of ultra-low frequency gravitational waves by monitoring pulsars and using radio telescopes. The advanced radio telescopes included India's uGMRT.

The waves detected originate from enormous black hole pairs found in colliding galaxies and create vibrations in the fabric of space-time.

The team's findings represent a significant breakthrough in the understanding of gravitational waves and created new opportunities for exploration in astrophysics.

The research, published in two papers in the Astronomy and Astrophysics journal, suggests the presence of these gravitational waves in the data collected by the European Pulsar Timing Array (EPTA) and Indian Pulsar Timing Array (InPTA) consortia.

 

How were these waves detected?

To detect these light-year-scale ripples, scientists used pulsars as cosmic beacons. Pulsars are rapidly rotating neutron stars, the remnants of dead stars, emitting regular radio beams as they rotate. By monitoring these pulsars using radio telescopes, such as India's uGMRT, researchers collected over 25 years of data, including three years of highly sensitive observations. The analysis of this unique dataset revealed consistent irregularities in the ticking rates of the monitored pulsars, indicating the influence of ultra-low frequency gravitational waves with oscillation periods ranging from one to ten years.

Nano-hertz frequency gravitational waves, as produced by dancing monster black hole pairs, offer insights into the secrets of the universe. These pairs form when galaxies merge, emitting gravitational waves at these astronomically long wavelengths. Additionally, other phenomena that occurred shortly after the birth of the universe can also generate waves at these frequencies.

A Gopakumar, chair of the InPTA consortium, stated that this marks the first time data from an Indian telescope has been used to hunt for gravitational waves.

“The results presented today mark the beginning of a new journey into the Universe to unveil some of these mysteries," he added.

Future prospects of research

The researchers are already collaborating under the International Pulsar Timing Array (IPTA) to combine their data sets. This collaboration aims to incorporate over 100 pulsars into the array, enabling even more sensitive observations and potentially unlocking further insights into the early universe and its associated phenomena.

The recent results are based on a coordinated effort among five major radio telescopes in Europe and the upgraded Giant Metrewave Radio Telescope in India. Analysis of the European and Indian Pulsar Timing Array (EPTA+InPTA) data revealed a common signal across the pulsars, indicating the presence of gravitational waves. Similar findings have been reported by other PTA collaborations worldwide, including Australia (PPTA), China (CPTA), and North America (NANOGrav).

The InPTA experiment involves researchers from various institutions in India, including NCRA, TIFR, IIT Roorkee, IISER Bhopal, IIT Hyderabad, IMSc Chennai, and RRI Bengaluru, in addition to their colleagues from Kumamoto University, Japan.

Jaikhomba Singha, a senior PhD scholar from IIT Roorkee who was a part of the research team said, “This is an extremely exciting time for early career researchers. We are in an era where an international team of researchers across the globe are all collaborating and trying to listen to the humming of our universe. The present results will open a plethora of exhilarating science for us in future."

The detection of gravitational-wave signals relies on a collaboration called the Pulsar Timing Array (PTA). By leveraging the stability of numerous pulsars distributed across the Milky Way galaxy, astronomers create a galactic-scale gravitational wave detector. Precise measurements of the arrival times of pulsar signals, spanning decades, are compared to study the effects of gravitational waves. These waves slightly alter the arrival times of radio pulses, enabling the detection of variations at a frequency ten billion times slower than the waves initially observed in 2015 by the Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors in the United States.