Have you ever wondered where does gold come from? Well, a cosmic cooking pot could probably be the answer. When scientists detected for the first time light tied to a gravitational-wave event, this was discovered. Thanks to two merging neutron stars located about 130 million light-years from the Earth in the constellation named Hydra.

"For the first time ever, we measured spacetime ripples (gravitational waves) and light from the same source in the universe," Karan Jani, an Indian-born astrophysicist and part of the LIGO (Laser Interferometer Gravitational-wave Observatory) team that made this discovery, told IANS.

Crashing neutron stars may be the universe's dominant source for many of the heaviest elements, including platinum and gold. "The collision provides us clues on how heavy elements like gold and platinum are produced in our cosmos," Jani said.

"Each element of gold that we love to show off in our jewellery, has reached our Earth after traveling from such collision of neutron stars from millions of light years from galaxies far far away. Yes, all of us carrying the pride of wearing gold are carrying relics from such cosmic events," he added.

On August 17, LIGO in the US, working with the Virgo Interferometer in Italy, detected gravitational waves passing the Earth. This event following the neutron star merger was named GW170817.

About two seconds later, two space observatories, NASA's Fermi Gamma-ray Space Telescope and European Space Agency's INTErnational Gamma Ray Astrophysics Laboratory (INTEGRAL), detected a short gamma-ray burst from the same area of the sky.

Several scientific papers describing and interpreting these observations have now been published in the journal Science, Nature, Physical Review Letters and The Astrophysical Journal.

Neutron stars are one of the smallest stars in the universe and form when a star much more massive than the Sun runs out of nuclear fuel and collapses to form an extremely dense and small object.

It is heavier than the Sun but its diameter is the size of an average city like Kolkata.

Such is the density of these bodies that a spoon of neutron star material can be as heavy as Mount Everest.

"The process (merger of neutron stars) leaves signatures in both gravitational and electromagnetic waves whose detection and exploration can potentially revolutionise our understanding of the universe," said Dibyendu Nandi, head, Center of Excellence in Space Sciences India (CESSI) at IISER Kolkata.

"The very high energy released in this process sustains exotic phenomena that may have produced a major fraction of the gold in the universe," he said.

As many 40 scientists from 13 Indian institutions are part of the LIGO-Virgo discovery paper, according to Tarun Souradeep, LIGO India spokesperson.

This discovery is also extremely significant given that this is the first time that both gravitational and electromagnetic waves from a cosmic event were detected together, said Nandi.

"We now get to see both sides of the coin," Nandi told IANS.

The neutron stars merged in a galaxy called NGC 4993.

"This detection is significant in three remarkable ways - first, it allows us to independently test Einstein's General Theory of Relativity as we recorded two different forms of radiation - gravitational waves and light - originating from the same astrophysical source," Jani said.

"Secondly we were able to constrain the expansion of our universe and subsequently measure the age of our universe, and thirdly the collision provides us clues on how heavy elements like gold and platinum are produced in our cosmos," he added.

Indian scientists contributed to the fundamental algorithms crucial to search for inspiraling binaries in noisy data from multiple detectors, computing waveforms for these signals by solving Einstein's equations, tests of Einstein's theory and many other aspects of the data analysis, said Souradeep.

In addition, several Indian telescopes such as AstroSat, Giant Metrewave Radio Telescope (GMRT) and the Himalayan Chandra Telescope (HCT) participated in the search for electromagnetic flashes.

The sensitive CZTI instrument on AstroSat helped narrow down the location of the gamma-ray flashes. HCT obtained optical images at locations of neutrinos detected by other telescopes at the same time as the burst, and showed that they were unrelated to the gravitational-wave trigger.

The sensitive CZTI instrument on AstroSat helped narrow down the location of the gamma-ray flashes. HCT obtained optical images at locations of neutrinos detected by other telescopes at the same time as the burst, and showed that they were unrelated to the gravitational-wave trigger.

The Indian team in LIGO includes scientists from CMI Chennai, ICTS-TIFR Bangalore, IISER Kolkata, IISER Trivandrum, IIT Bombay, IIT Gandhinagar, IIT Hyderabad, IIT Madras, IPR Gandhinagar, IUCAA Pune, RRCAT Indore, TIFR Mumbai and UAIR Gandhinagar.

Astronomers from IISER Pune, IIT Bombay, IUCAA Pune, TIFR Mumbai, PRL Ahmedabad, IIT Hyderabad, IIA Bangalore, NCRA-TIFR Pune, ARIES Nainital and IIST Trivandrum participated in the electromagnetic follow-up of this event using a variety of telescopes.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier in October.

Dr. Karan Jani is a Vadodara-born astrophysicist and part of the LIGO team that made this discovery. For his research on gravitational waves, Forbes listed Jani as one of the 30 scientists under 30 that are changing the world and was a recipient of the 2016 Special Breakthrough Prize in Fundamental Physics. He was also invited to meet the Hon. PM of India, Shri Narendra Modi, on the role of expanding LIGO research in India. Pioneers of the LIGO experiment were awarded the 2017 Nobel Prize in Physics.

Dr Jani says:

“What a time to be alive and be doing science!”

“For the first time ever, we measured spacetime ripples (aka gravitational waves) and light from the same source in the universe! Our understanding of light and gravity fundamentally changed a century ago thanks to Albert Einstein’s Theory of Relativity, and the fact that today we see events in the universe where both these concepts are so elegantly intertwined would have brought smile on Einstein’s face.”

“Along with the gravitational detectors LIGO (US) and Virgo (Europe), some 70 observatories and telescope around the world (and space) allowed us to measure the collision two neutron stars. These stars are about the mass of our Sun, but has a radius of just about 15 km, making them the most extreme matter objects in the universe.”

"This detection is significant in three remarkable ways - first, it allows us to independently test Einstein's General Theory of Relativity as we are recorded two different form of radiation - gravitational waves and light - originating from the same astrophysical source, secondly we were able to constrain the expansion of our universe and subsequently measure the Age of our Universe, and thirdly the collision provides us clues on how heavy elements like gold and platinum are produced in our cosmos. Each element of gold that we love to show off in our jewellery, has reached our earth after traveling from such collision of neutron stars from millions of light years from galaxies far far away. Yes, all of us carrying the pride of wearing gold are carrying relics from such cosmic events!"

"This discovery opens up the long-awaited era of multimessenger astronomy. As a scientist, It is very reassuring to see that India is investing in a field that is just beginning. In future, with LIGO-India we will be able to more precisely constrain the sky-location of such events as well as the extreme matter physics of such neutron stars.”

“Building such mega-science projects allows Indian universities to participate in cutting-edge research, which ultimately trickles down all the way to impacting undergraduate education. Imagine first-year college students from local colleges and state universities analyzing spacetime rhythms from events that occurred even before life started on this planet!”

“In combination of other grand science projects, including India's very own space observatory ASTROSAT as well funding one of world's biggest telescope (Thirty Metre Telescope), I can proudly say there has never been a better time to do space related science in India."

—with inputs from IANS

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