Scientists 'see' gravitational waves with telescope

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Scientists announced on Monday that they have detected gravitational waves from a never-before-seen merger of two neutron stars.

Previous wave detections were from the mergers of black holes – events that did not emit light. But Monday's phenomenon was detectable by regular light telescopes.

The measurements of light and other energy forms emanating from the merger of the two neutron stars 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.

Image made by Caltech and NASA shows the evolution of neutron star merger confirming heavy element synthesis. /Xinhua Photo

The event took place 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 tons, danced ever faster and closer together until they collided, said Carnegie Institution astronomer Maria Drout.

Called kilonova, the crash 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 crash happened 130 million years ago, while dinosaurs still roamed on Earth, but the signal didn’t arrive on Earth until Monday after traveling 130 million light-years.

A light-year is 5.88 trillion miles.

Signals were picked up within 1.7 seconds of each other by NASA’s Fermi telescope, which detects gamma rays, and gravity wave detectors in Louisiana and Washington states that are a part of the LIGO Laboratory, whose founders won a Nobel Prize earlier this month.

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 analyze: matter, light, and other radiation.

Finding where the crash happened was no easy task. Eventually, scientists narrowed the location down to 100 galaxies, began a closer search of those, and found it in the ninth galaxy they looked at.

Origin of heavy elements

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.

Image made by Caltech shows Periodic Table indicating which elements originate in neutron star mergers. /Xinhua Photo

“We see the gold being formed,” said Syracuse University physics professor Duncan 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, said David Reitze of the California Institute of Technology and the executive director of the Laser Interferometer Gravitational-Wave Observatory – maybe ones with rich veins of precious metals.

“We already knew that iron came from a stellar explosion, the calcium in your bones came from stars and now we know the gold in your wedding ring came from merging neutron stars,” said University of California Santa Cruz’s Ryan Foley.

The deadly gamma ray

The crash also helped explain the origins of one of the most dangerous forces of the cosmos – short gamma ray bursts, focused beams of radiation that could erase life on any planet that happened to get in the way. These bursts shoot out in two different directions perpendicular to where the two neutron stars first crash, Reitze said.

Luckily for us, the beams of gamma rays were not focused on Earth and were generated too far away to be a threat, he said.

The expansion of the universe

Scientists knew that the universe has been expanding since the Big Bang. By using LIGO to measure gravitational waves while watching this event unfold, researchers came up with a new estimate for how fast that is happening, the so-called Hubble Constant.

Before this, scientists came up with two slightly different answers using different techniques. The rough figure that came out of this event is between the original two, Reitze said.

Illustration shows two merging neutron stars. /Xinhua Photo

The first optical images showed a bright blue dot that was very hot, which was likely the start of the heavy element creation process amid the neutron star debris, Drout said. After a day or two that blue faded, becoming much fainter and redder. And after three weeks it was completely gone, she said.

This almost didn’t happen. Eight days after the signal came through, the LIGO gravitational waves were shut down for a year’s worth of planned upgrades. A month later the whole area where the crash happened would have been blocked from astronomers’ prying eyes by the sun.

Scientists involved with the search for gravitational waves said this was the event they had prepared for over more than 20 years.

The findings are “of spectacular importance,” said Penn State physicist Abhay Ashtekar, who wasn’t part of the research.

“This is really brand new.”

Almost all of the discoveries confirmed existing theories, but had not been proven – an encouraging result for theorists who have been trying to explain what is happening in the cosmos, said France Cordova, an astrophysicist who directs the National Science Foundation.

“We so far have been unable to prove Einstein wrong,” said Georgia Tech physics professor Laura Cadonati. “But we’re going to keep trying."

China's HXMT caught the best image

Xiong Shaolin, a researcher at Institute of High Energy Physics of CAS, is very proud of China's participation in this great discovery.

“Dozens of telescopes from around the world have tried to observe this phenomenon, but only four of them actually saw it at high frequency,” he said.

Among the four, the Hard X-ray Modulation Telescope (HXMT) of China has the one of best image resolution, which makes its data crucial and irreplaceable, Xiong added.

This achievement indicates China’s role in this massive space collaboration has moved from observation to participation.

Source(s): AP