Giant Metrewave Radio Telescope (GMRT)
The Giant Metrewave Radio Telescope (GMRT), located near Narayangaon, Pune in India.
It is an array of thirty fully steerable parabolic radio telescopes of 45 metre diameter, observing at metre wavelengths.
It is the largest and most sensitive radio telescope array in the world at low frequencies.
It is operated by the National Centre for Radio Astrophysics (NCRA), a part of the Tata Institute of Fundamental Research, Mumbai.
It was conceived and built under the direction of Late Prof. Govind Swarup during 1984 to 1996.
It was recently upgraded with new receivers, after which it is also known as the upgraded Giant Metrewave Radio Telescope (uGMRT).
Observations of GMRT
One of the aims for the telescope during its development was to search for the highly redshifted 21-cm line radiation from primordial neutral hydrogen clouds in order to determine the epoch of galaxy formation in the universe.
Astronomers from all over the world regularly use this telescope to observe many different astronomical objects such as HII regions, galaxies, pulsars, supernovae, and Sun and solar winds.
In August 2018, the most distant galaxy ever known, located at a distance of 12 billion light years, was discovered by GMRT.
In February 2020, it helped in the observation of the biggest explosion in the history of the universe, the Ophiuchus Supercluster explosion.
In January 2023, the telescope picked up a radio signal which originated from 8.8 billion light years away.
GMRT was among the world’s six large telescopes that played a vital role in providing evidence confirming the presence of gravitational waves using pulsar observations.
An international team of astronomers from India, Japan and Europe has published the results from monitoring pulsars, called ‘nature’s best clocks’.
These results 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 expected to originate from a large number of dancing monster black hole pairs, crores of times heavier than our sun.
What are Gravitational Waves?
Gravitational waves are ripples in space-time caused by some of the most violent and energetic processes in the Universe.
Albert Einstein predicted the existence of gravitational waves in 1916 in his general theory of relativity.
Einstein's mathematics showed that massive accelerating objects would disrupt space-time in such a way that waves of undulating space-time would propagate in all directions away from the source.
These massive objects include things like neutron stars or black holes orbiting each other.
These cosmic ripples would travel at the speed of light, carrying with them information about their origins, as well as clues to the nature of gravity itself.
The strongest gravitational waves are produced by cataclysmic events such as colliding black holes, supernovae (massive stars exploding at the end of their lifetimes), and colliding neutron stars.
Other gravitational waves are predicted to be caused by the rotation of neutron stars that are not perfect spheres.
Possibly even the remnants of gravitational radiation created by the Big Bang.
Laser Interferometer Gravitational-Wave Observatory (LIGO), which made the first direct detection of gravitational waves in 2015.
What are pulsars?
Pulsars are a type of rapidly rotating neutron stars that are essentially embers of dead stars which are present in our galaxy.
A pulsar is like a cosmic lighthouse as it emits radio beams that flashes by the Earth regularly akin to a harbour lighthouse.
As these signals are accurately timed, there is a great interest in studying these pulsars and to unravel the mysteries of the Universe.
In order to detect gravitational wave signals, scientists explore several ultra-stable pulsar clocks randomly distributed across our Milky Way galaxy and create an ‘imaginary’ galactic-scale gravitational wave detector.
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