The Giant Metrewave Radio Telescope (GMRT) Observatory is an array of 30 fully steerable parabolic radio telescopes of 45-meter diameter each. Located near Pune in India, it observes the cosmic wonders at meter wavelength. It is operated by NCRA (National Centre for Radio Astrophysics), a part of TIFR, Mumbai. One of the most sensitive telescopes in the world (within its range), the GMRT has an effective diameter of 25 kilometers and comprises 30 smaller dish antennas.

Giant Metrewave Radio Telescope (GMRT) (Image: NCRA-TIFR)
Giant Metrewave Radio Telescope (GMRT) (Image: NCRA-TIFR)

Primary goals of GMRT

When GMRT was under construction, its primary aim was to search for the highly red-shifted 21-cm line radiation from primordial neutral hydrogen clouds. To explore the mysteries hidden in the dark sky, one would like to study the sky at a wider range of frequencies. However, some important observations can only be made at low radio frequencies, and this is where GMRT helps the most.

For example, pulsars appear to be extremely bright at low frequencies but become faint as one moves to higher frequencies. The study of pulsars is significant to understand regions of extremely high densities, the physics of strong gravitational fields, and even to detect the presence of gravitational waves. The GMRT also aims to search for the Epoch of Reionization, which occurred around a billion years after the Big Bang and was an important milestone in creating the universe.

What has GMRT discovered so far

Ring of H2 Gas: Over the years, GMRT has carved a niche for itself in the regime of radio astronomy by making some of the most remarkable observations. Once, a team of astronomers working with GMRT discovered a mysterious ring of H2 gas around a distant galaxy. The ring was found to be much bigger than the galaxy it was surrounding and had a diameter of about 380,000 light-years (about 4 times that of our Milky Way).

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The galaxy (named AGC 203001) flaunting such a ring is 260 million light-years away. There is only one other such known system with such a large neutral hydrogen ring. The origin and formation of such rings is still a matter of debate among astrophysicists. The neutral hydrogen is known to emit radio waves at a wavelength of about 21 cm. This particular radiation from neutral hydrogen atoms has allowed radio astronomers to map the amount and distribution of neutral hydrogen gas in galaxies, including our Milky Way.

Youngest Supernova Remnant In Milky Way: Another marvelous discovery made by GMRT has been that of the youngest supernova remnant within our Galaxy. The stars, which are much heavier than our Sun, die by a phenomenon known as a supernova explosion. Such explosions generate energies more than the galaxy’s entire energy output for the first few days and fade rapidly thereafter. In the recent 400 years, about a dozen supernovas should have taken place. But due to technological limitations, only two of them have been discovered to date.

Various groups across the world are trying to find more supernova remnants. The major reason for not discovering the expected number of supernova remnants is the lack of telescopes that can search with better sensitivity and resolution. The GMRT is thriving to make these rare and difficult observations possible!

Most Distant Radio Galaxy: Finding distant galaxies is another task most astronomers are working upon. And GMRT is proving out to be instrumental in this search as well. In 2018, Astronomers discovered the most distant radio galaxy ever known with the help of the GMRT. Located at a distance of 12 billion light-years, the galaxy is from a time when the universe was only seven percent of its current age. The distance to this galaxy was then determined using the Gemini North telescope in Hawaii and the Large Binocular Telescope in Arizona.

IEEE milestone status:

The IEEE or the Institute of Electrical and Electronics Engineers, headquartered in New Jersey, United States, is the world’s largest technical professional organization dedicated to advancing technology in all areas related to electrical and electronics engineering. The IEEE Milestones program honors significant technical achievements that have a global or regional impact in all areas associated with IEEE. Recently, IEEE recognized the global impact of GMRT, with users from 40+ countries worldwide, and acknowledged that it was designed and built entirely in India, with some of the most innovative and brilliant ideas.

The IEEE Milestone will be formalized in a special dedication ceremony involving unveiling the bronze citation plaque at the GMRT premises. The event is likely to take place sometime this year. GMRT is only the third such contribution from India to be recognized as an IEEE Milestone recognition. The previous two are the pioneering work done by Sir J. C. Bose to demonstrate the generation and reception of radio waves in 1895 and the Nobel Prize-winning discovery by Sir C.V. Raman in 1930.

Every great achievement is impossible without nourishing the basic idea behind it. Regarded as the “Father of Indian Radio Astronomy”, Govind Swarup was the founder-director of TIFR – National Centre for Radio Astrophysics (NCRA) in Pune. It was Swarup who conceptualized the ideas and led the teams that eventually set up the Ooty Radio Telescope (ORT) and Giant Meterwave Radio Telescope (GMRT).

How Is This Radio Telescope In Pune Changing Our Understanding Of The Universe? 1
Prof. Govind Sarup (Image: NCRA)

Astronomers worldwide regularly use GMRT to observe many different astronomical objects such as HII regions, galaxies, pulsars, supernovae, and Sun and solar winds. GMRT has been an important asset in our quest to explore this universe and is expected to unveil some of the deepest mysteries of the universe in the future.

This article on GMRT is a guest article by Krishna Bhutada, an Engineering student from Pune, India.

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