WASHINGTON: It was a faint signal, but it told of one of the most violent acts in the universe, and it would soon reveal secrets of the cosmos, including how gold was created.

Astronomers around the world reacted to the signal quickly, focusing telescopes located on every continent and even in orbit to a distant spot in the sky.

What they witnessed in mid-August and revealed on Monday was the long-ago collision of two neutron stars a phenomenon California Institute of Technology’s David H. Reitze called “the most spectacular fireworks in the universe”.

“When these things collide, all hell breaks loose,” he said. Measurements of the light and other energy emanating from the crash have helped scientists explain how planet-killing gamma ray bursts are born, how fast the universe is expanding, and where heavy elements like platinum and gold come from.

“This is getting everything you wish for,” said Syracuse University physics professor Duncan Brown, one of more than 4,000 scientists involved in the blitz of science that the crash kicked off. “This is our fantasy observation.”

It started in a galaxy called NGC 4993, seen from Earth in the Hydra constellation. Two neutron stars, collapsed cores of stars so dense that a teaspoon of their matter would weigh one billion tonnes, danced ever faster and closer together until they collided, said Carnegie Institution astronomer Maria Drout.

The crash, called a kilonova, generated a fierce burst of gamma rays and a gravitational wave, a faint ripple in the fabric of space and time, first theorized by Albert Einstein.

The signal arrived on Earth on Aug 17 after travelling 130 million light-years. A light-year is 5.88 trillion miles.

Nasa’s Fermi telescope, which detects gamma rays, sent out the first alarm. Then, 1.7 seconds later, gravity wave detectors in Louisiana and Washington state that are a part of the LIGO Laboratory , whose founders won a Nobel Prize earlier this month, detected the crash. It issued a worldwide alert to focus telescopes on what became the most well-observed astronomical event in history.

Before August, the only other gravity waves detected by LIGO were generated by colliding black holes. But black holes let no light escape, so astronomers could see nothing.

This time there was plenty to see, measure and analyse: matter, light, and other radiation. The Hubble Space Telescope even got a snapshot of the afterglow.

“The completeness of this picture from the beginning to the end is unprecedented,” said Columbia University physics professor Szabolcs Marka. “There are many, many extraordinary discoveries within the discovery.”

The colliding stars spewed bright blue, super-hot debris that was dense and unstable. Some of it coalesced into heavy elements, like gold, platinum and uranium. Scientists had suspected neutron star collisions had enough power to create heavier elements, but weren’t certain until they witnessed it.

“We see the gold being formed,” said Syracuse’s Brown.

Calculations from a telescope measuring ultraviolet light showed that the combined mass of the heavy elements from this explosion is 1,300 times the mass of Earth. And all that stuff including lighter elements was thrown out in all different directions and is now speeding across the universe.

Perhaps one day the material will clump together into planets the way ours was formed, Reitze said maybe ones with rich veins of precious metals.

Published in Dawn, October 17th, 2017