India’s largest radio telescope plays vital role in detecting universe’s vibrations

Subject : Science and technology

Section: Space technology

Concept :

Recently, an international team of astronomers announced scientific evidence confirming the presence of gravitational waves using pulsar observations.
India’s Giant Metrewave Radio Telescope (GMRT) was among the world’s six large telescopes that played a vital role in providing this evidence.

Analysing the signals from pulsars

Nicknamed as cosmic clocks, pulsars are rapidly spinning neutron stars that send out radio signals at regular intervals which are seen as bright flashes from the Earth.
As these signals are accurately timed, there is a great interest in studying these pulsars and to unravel the mysteries of the Universe.

How analysis is done?

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.
There are several signals travelling through spacetime of the Universe.
But, the presence of gravitational waves influences the arrival of these signals when detected from Earth.
It was noticed that some signals arrive early while others, with a slight delay (less than a millionth of a second).

What has been detected?

Nano-hertz signals were heard as humming from the Universe.
It is expected that ultra-low frequency gravitational waves, also known as nano-hertz gravitational waves, emerge from a colliding pair of very large monster black holes, many crores of times heavier than our Sun.
The signals or ripples that emerge from within these blackholes are known as nano-hertz gravitational waves.
Their wavelengths can be many lakhs of crores of kilometres and oscillate with a periodicity anywhere between a 1 year to 10 years.
When there is continuous arrival of these nano-hertz gravitational waves, it creates a consistent humming in our Universe, which gets detected using powerful radio telescopes from the Earth.
These were caused due to the presence of gravitational waves and due to signal irregularities emerging from pulsars.

Giant Metrewave Radio Telescope (GMRT)

GMRT is a low-frequency radio telescope that helps investigate various radio astrophysical problems ranging from nearby solar systems to the edge of the observable universe.
Located at Khodad, 80 km north of Pune, the telescope is operated by the National Centre of Radio Astrophysics (NCRA).
NCRA is a part of the Tata Institute of Fundamental Research (TIFR), Mumbai.
GMRT is a project of the Department of Atomic Energy (DAE), operating under the Tata Institute of Fundamental Research (TIFR).
It consists of 30 fully- steerable dish type antennas of 45-meter diameter each, spread over a 25-km region.
GMRT is presently the world’s largest radio telescope operating at meter wavelength.

Objectives of GMRT

GMRT is a very versatile instrument for investigating a variety of radio astrophysical problems.
Two of its most important astrophysical objectives are:
to detect the highly redshifted spectral line of neutral Hydrogen expected from proto-clusters or protogalaxies before they condensed to form galaxies in the early phase of the Universe;
Redshift represents the signal’s wavelength change depending on the object’s location and movement.
to search for and study rapidly-rotating Pulsars in our galaxy.
Pulsars are rapidly rotating neutron stars with extremely high densities.
A pulsar is like a cosmic lighthouse as it emits radio beams that flashes by the Earth regularly akin to a harbour lighthouse.