Scientists witness huge cosmic crash, find origins of gold

[JustJohn or JJ]

Scientists witness huge cosmic crash, find origins of gold

SETH BORENSTEIN
Associated PressOctober 16, 2017

This illustration provided by the Carnegie Institution for Science depicts the collision of two neutron stars
detected on Aug. 17, 2017. The explosion threw matter, light, radiation and gravitational waves into space.
The discovery was reported on Monday, Oct. 16, 2017. (Robin Dienel/Carnegie Institution for Science via AP)


WASHINGTON (AP) — 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 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 1 billion tons, 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 traveling 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 analyze: 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.

"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 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.

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.

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.

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."

[JustJohn or JJ]

Einstein’s waves detected in star smash

By Pallab Ghosh Science correspondent, BBC News, Louisiana


Artwork: Merging neutron stars rippling across space-time


Scientists have detected the warping of space generated by the collision of two dead stars, or neutron stars.

They have confirmed that such mergers lead to the production of the gold and platinum that exists in the Universe.

The measurement of the gravitational waves given off by this cataclysmic event was made on 17 August by the LIGO-VIRGO Collaboration.

The discovery enabled telescopes all over the world to capture details of the merger as it unfolded.

David Reitze, executive director of the LIGO Laboratory at Caltech in Pasadena, California, said: "This is the one we've all been waiting for."

The outburst took place in a galaxy called NGC 4993, located roughly a thousand billion, billion km away in the Constellation Hydra.

It happened 130 million years ago - when dinosaurs roamed the Earth. It was so far away that the light and gravitational waves have only just reached us.

The stars themselves had masses 10-20% greater than our Sun - but they were no larger than 30km across.

They were the crushed leftover cores of massive stars that long ago exploded as supernovas.

They are called neutron stars because the process of crushing the star makes the charged protons and electrons in the atoms of the star combine - to form an object made entirely of neutrons.

Such remnants are incredibly dense - a teaspoonful would weigh a billion tonnes.

In the landscaped campus of one of the laboratories that made the detection, a fountain sprays jets of water skyward which are then pulled back down by gravity, sending ripples across the crystal clear pond.

The LIGO detector, sitting incongruously in the vast woodland of Livingston in Louisiana, was designed to detect the gravitational ripples across the Universe created by cataclysmic cosmic events.

Since it was upgraded two years ago, it has four times sensed the collisions of black holes.

Gravitational waves caused by violent events send ripples through space-time that stretch and squeeze everything they pass through by a tiny amount - less than the width of an atom.

The LIGO lab at Livingston consists of a small building with two, two-and-a-half-mile pipelines stretching out at right angles. Inside each pipe is a powerful laser accurately measuring any change in its length.

I walk along one of the pipes with Prof Norna Robertson, a Scot who used to work at Glasgow University - and more recently helped to design the instrument's detection system.

Prof Robertson's work has helped the LIGO-VIRGO Scientific Collaboration to make the first ever detection of the gravitational waves given off by the collision of two neutron stars.

"I'm really thrilled about what we have done. I started off as a student in Glasgow 40 years ago working on gravitational waves. It's been a long long road; there have been some ups and downs but now it's all come together," she told BBC News.

"These last couple of years, first of all with the detection of black holes mergers and now a neutron star merger, I really feel we are opening up a new field, and that's what I wanted to do and now we've done it."

The detection enabled 70 telescopes to obtain the first ever detailed pictures of such an event.

These show an explosion 1,000 times more powerful than a supernova - a burst called a kilonova.

Researchers had suspected that this huge release of energy leads to the creation of rare elements, such as gold and platinum.

Dr Kate Maguire, from Queen's University Belfast, who analysed the collision's burst of light, said that the theory was now proven.

"Using some of the world's best telescopes, we have discovered that this neutron star merger scattered heavy chemical elements, such as gold and platinum, out into space at high speeds.

"These new results have significantly contributed to solving the long-debated mystery of the origin of elements heavier than iron in the periodic table."
Improvements coming

It was also direct confirmation that short bursts of gamma-ray radiation are linked to colliding neutron stars.

By combining information from gravitational waves and the light collected by telescopes, researchers also used a new technique to measure the expansion rate of the Universe. This technique was first proposed in 1986 by the University of Cardiff's Prof Bernard Schutz.

Prof Stephen Hawking of Cambridge University told BBC News that this was "the first rung of a ladder" for a new method of measuring distances in the Universe.

"A new observational window on the Universe typically leads to surprises that cannot yet be foreseen. We are still rubbing our eyes, or rather ears, as we have just woken up to the sound of gravitational waves," he said.


The LIGO Louisiana lab has 4km-long pipes running out from its control centre

Prof Nial Tanvir, from Leicester University, uses the VISTA telescope in Chile.

He and his colleagues started searching for the neutron star collision as soon as they heard of the gravitational wave detection.

"We were really excited when we first got notification that a neutron star merger had been detected by LIGO," he said. "We stayed up all night analysing the images as they came in, and it was remarkable how well the observations matched the theoretical predictions that had been made."

LIGO is now being upgraded. In a year's time it will be twice as sensitive - and so will be able to scan eight times the volume of the space.

The researchers believe that detections of black holes and neutron stars will become common place. And they hope that they will begin to detect objects that they currently cannot even imagine and so usher in a new era of astronomy.