Chinese telescope in unique position for stellar merger

Pablo Tucker
October 16, 2017

For Berger and the rest of the Dark Energy Camera follow-up team, it was time to call in the Hubble Space Telescope.

The discovery has consumed the astronomical community in recent weeks.

Gold: "We can probably account for all the gold that has ever been made", O'Shaughnessy said.

In research published in three different journals today (Nature, Nature Astronomy and Astrophysical Journal Letters), hundreds of physicists and collaborators outline a first-of-its-kind observation: the elusive neutron star merger.

As the data trickled in from the various instruments, the collected data set was becoming more and more astounding. Astronomers worked together to locate the area where the merger occurred. A teaspoon of neutron star would weigh as much as one billion tons.

"When the stars die, that creates new things", Smith said. The findings are "in excellent agreement with the models of binary-neutron-star formation", Berger said.


Advanced LIGO's two 4km detectors in the United States have been operating since 2015. Researchers first suspected a secret nuclear test conducted by the Soviet Union. They're also wondering why the gamma ray burst was only two seconds long.

Less than 11 hours after the gravitational-wave detectors sounded the alarm, astronomers had their first glimpse of this never-before-seen event involving the neutron stars. There was no way to directly check until now.

Meanwhile, NASA's orbiting gamma ray telescopes Fermi and Swift continued their continuous monitoring of the skies.

If the acronym LIGO isn't in your repertoire, it stands for Laser Interferometer Gravitational-Wave Observatory. "We believe we're seeing the creation of elements whose origin has been a mystery up until now". "It's really the first direct compelling connection between these two phenomena".

About 12 years ago, Daniel Holz and I examined how well this idea could be implemented, focusing on how it could be done if the gravitational waves were accompanied by some electromagnetic signature, such as a short-hard gamma-ray burst. "It's just too early to say, and I'm not holding back".

"Witnessing this event makes that more likely", OzGrav scientist Dr Kendall Ackley from Monash University said. According to that thinking, the crash of neutron stars ejects matter in what's called a kilonova. "He was able to create a theory that was so dramatically new that 100 years later we're still trying to prove some of it's most dramatic predictions". Signals of other forms of light, or electromagnetic radiation-X-ray, ultraviolet, optical, infrared and radio waves-were also detected. Produced when the largest stars come of the end of their life, run out of fuel and collapse in on themselves, neutron stars are the smallest and most dense stars can get. Until now, they'd made only four such detections, and each time the distortions in space-time were caused by the collision of two black holes. Just one teaspoon of neutron star material is as heavy as the Great Pyramid of Giza.


Future observations of neutron-star mergers will settle these questions.

As the neutron stars spiraled in, they produced gravitational waves.

"We started scanning the region of the sky where LIGO told us the gravitational waves came from, and it took us 45 minutes until we found it", says Edo Berger, an astronomer at the Harvard-Smithsonian Center for Astrophysics. Those working on data from the merger have confirmed that the constant is about 70 kilometres per second per megaparsec, a value which is consistent with previous estimates.

To improve the measurement, scientists will have to spot many more neutron-star mergers.

LISA will be sensitive to gravitational waves at much lower frequencies than LIGO and Virgo can measure. "It is clear that the rate of occurrence is somewhat higher than expected", he said.

The discoveries are being hailed by astrophysicists as the most important of a generation and for most a once in a career event. "It will be tremendously exciting".


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