Scientists Say Universe Has A Background Hum
WHAT HAS HAPPENED?
In a major breakthrough, a global team of astronomers that included scientists from seven Indian institutes have, for the first time, Heard the low-pitch "hum” of gravitational waves reverberating across the universe, the existence of which was predicted by Albert Einstein. India's upgraded Giant Metrewave Radio Telescope (uGMRT) near Pune was one of the world's six most sensitive radio telescopes that played a key role in discovering the persistent hum.
The gravitational waves (GW) are thought to have originated from the merger of supermassive black holes in the early universe, soon after the Big Bang. With this discovery, scientists hope to learn more about physical reality and answer mysteries about the nature of merging supermassive black holes and what brings them together.
ABOUT THE FINDINGS
The findings, reported in a series of papers in The Astrophysical Journal Letters on Thursday,
Come from 15 years of observations made by the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) with more than 190 scientists, Including from the Indian Pulsar Timing Array (InPTA) that used gMRT.
ROLE OF INDIAN TELESCOPE
The Indian telescope was used to collect and correct the signal and increase the accuracy of the signal so that it could corroborate the "hum" of the universe, as detected by their European counterparts. The first experiment of the pulsar timing array started in 2002 and InPTA got involved in 2016. The InPTA experiment involves researchers from NCRA (Pune), TIFR (Mumbai), IIT (Roorkee), IISER (Bhopal), IIT (Hyderabad), IMSc (Chennai) and RRI (Bengaluru) along with their colleagues from Kumamoto University, Japan.
LIGO VS NANOGRAV
Gravitational waves were first proposed by Einstein in 1916 but were not directly detected until about 100 years later when the National Science Foundation-funded LIGO in 2016 picked up the waves from a pair of distant colliding black holes. However, LIGO detected gravitational waves that were much higher in frequency than those registered by NANOGrav.
WHERE DO GRAVITATIONAL WAVES COME FROM?
Supermassive black holes in almost all galaxies weigh several million to many billion times the mass of the Sun. When galaxies merge, black holes are also expected to merge after a long spiral dance. Merging black holes emit gravitational waves
WHAT IS HUMMING?
When black holes merge across the universe and in every direction, these waves overlap and form a background hum of gravitational waves.
This thrumming hum is called stochastic gravitational wave background.
WHY SHOULD WE CARE ABOUT GRAVITATIONAL WAVES?
Pretty much everything that we know about faraway objects, or those too small to be seen, has come through the detection of the electromagnetic waves either emitted or reflected by them. These electromagnetic waves, of which visible light is also a part, very often carry information that is characteristic of the objects they are emitted. Over the years, we have built different kinds of detectors to trap these waves and read the information they are carrying.
But as almost 95% of the universe is known to consist of dark matter and dark energy, which don’t emit any light or any other electromagnetic waves, most of the cosmos remains ‘invisible’ to astrophysicists and astronomers. This changed when scientists for the first time detected gravitational waves eight years ago. Like electromagnetic waves, gravitational waves, too, are thought to be
characteristic of the event that generated them. This is how scientists confirmed the existence of black holes, which can’t be ‘seen’.
Gravitational waves essentially give us the ability to ‘see’ what remains ‘invisible’ to us in the universe. They can tell us about our origin and answer fundamental questions about outer space, such as how different galaxies have emerged and evolved over the entire course of the universe.
