'We did not expect it to be confirmed within our lifetimes'

Israeli scientists predicted effects seen in historic neutron star study

The scientific community was skeptical following a 1989 paper positing that stars’ collision leads to the creation of heavy elements, like gold

Illustration of a neutron star. (Screen capture: YouTube, Hebrew University)
Illustration of a neutron star. (Screen capture: YouTube, Hebrew University)

Scientists have for the first time witnessed the crash of two ultra-dense neutron stars, researchers revealed Monday, confirming a long-ridiculed theory proposed by Israeli scientists 28 years ago on how heavy elements, such as gold, were created.

The Israeli scientists had predicted that when two neutron stars collide, in addition to making ripples in the fabric of space-time known as gravitational waves, they also create bright flashes of high-energy radiation called gamma ray bursts and form neutron-rich heavy elements such as gold, plutonium and uranium.

These predictions were confirmed with observations made in August and published by several teams on Monday, making international headlines.

Hebrew University’s Tsvi Piran speaks of his predictions of neutrino star collisions, October 16, 2017. (Screen capture: YouTube, Hebrew University)

In 1989, David Eichler of Ben Gurion University, Mario Livio of Haifa’s Technion, and David N. Schramms of University of Chicago, led by Hebrew University’s Tsvi Piran, published an article in Nature entitled, “Nucleosynthesis, neutrino bursts and gamma rays from coalescing neutron stars.”

In the article, they predicted that “such events should also synthesize neutron-rich heavy elements… Furthermore, these collisions should produce neutrino bursts and resultant bursts of gamma rays.”

“I am exhilarated by this confirmation of a prediction we made nearly 30 years ago,” said Piran following the announcement.  “I also remember how difficult it was to convince the scientific community of our idea — at the time it was against the standard model that was published even in freshman textbooks on astronomy.”

“When we made this prediction in 1989, we did not expect it to be confirmed within our lifetimes. But with continued curiosity and the development of new technologies, we are able learn ever deeper truths about the nature of our Universe.”

These predictions were initially met with skepticism and ignored. However, the recent groundbreaking observations fully confirmed the predictions.

The data finally revealed where much of the gold, platinum, mercury and other heavy elements in the universe came from.

Telescopes saw evidence of newly-forged material in the fallout, the teams said — a source long suspected, now confirmed.

Illustration of collision of two neutron stars. (Screen capture: YouTube, Hebrew University)

“It makes it quite clear that a significant fraction, maybe half, maybe more, of the heavy elements in the universe are actually produced by this kind of collision,” said physicist Patrick Sutton, a member of the Laser Interferometer Gravitational-Wave Observatory (LIGO) which contributed to the find.

The latest wave observation was accompanied by flashes of gamma rays, which scientists said came from closer in the universe and were less bright than expected.

“What this event is telling us is that there may be many more of these short gamma ray bursts going off nearby in the universe than we expected,” Sutton said.

“This might be the tip of the iceberg of short gamma ray bursts produced by collisions and mergers of neutron stars” — an exciting prospect for scientists hoping to uncover further secrets of the universe.

Illustration of collision of gravitational waves. (Screen capture: YouTube, Hebrew University)

The observation was the fruit of years of labor by thousands of scientists at more than 70 ground- and space-based observatories scattered around the globe.

Along with LIGO, they included teams from Europe’s Virgo gravitational wave detector in Italy, and a number of ground- and space-based telescopes, including NASA’s Hubble. Researchers included a team from Tel Aviv University.

“This is a milestone in the growing effort by scientists worldwide to unlock the mysteries of the universe and of earth,” said Ehud Nakar of Tel Aviv University, who along with his graduate student Ore Gottlieb led the theoretical analysis for studies published Monday in “Science” and “Nature.”

“This discovery has allowed astronomers to combine gravitational waves with light and produce a detailed model of the emission for the first time. This introduces a new era in astronomy,” says Gottlieb.

The detection is another feather in the cap for German physicist Albert Einstein, who first predicted gravitational waves more than 100 years ago.

Three LIGO pioneers, Barry Barish, Kip Thorne and Rainer Weiss, were awarded the Nobel Physics Prize this month for the observation of gravitational waves, without which the latest discovery would not have been possible.

The ripples have been observed four times before now — the first time by LIGO in September 2015.

The fifth and latest gravitational wave observation is the first from a neutron star fusion. The other four were from black hole mergers which are even more violent but unlike neutron stars, emit no light.

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