Noviembre 13, 2018

Unprecedented star collision observed through light and gravitational waves

17 Octubre 2017, 10:23 | Verda Sainz

Unprecedented star collision observed through light and gravitational waves

The LIGO gravitational-wave detectors in Hanford Washington, and Livingston Louisiana

Swinburne's Associate Professor, Jeffrey Cooke, a Chief Investigator with OzGrav, says the event will go down in history as the dawn of a new era of gravitational wave multi-messenger astronomy.

Rochester Institute of Technology researchers played a significant role in an worldwide announcement today that has changed the future of astrophysics. Either an even bigger neutron star is born or a black hole is made.

Scientists at the LIGO detectors and the world over detected the first "ripples in space" or gravitational waves produced by the merger of two ancient remnants of stars known as neutron stars. Its European counterpart, VIRGO, collaborated for the fourth detection.

This allowed astronomers to localise the event within hours and launch follow-up observations by Salt and numerous other telescopes in South Africa and around the world.

What's different this time is that the wave detection was matched by visual confirmation of the primeval collision. So astrophysicists at LIGO and VIRGO detected the motion from the collision, and astronomers saw the flash of light. These collisions are rare, which is why those elements (which include gold, platinum and uranium) are rare compared to lighter ones like hydrogen, carbon and oxygen.

But what exactly is it that scientists are so excited about?

The gravitational waves are an outcome of enormous events like merging of black holes or neutron stars, and appear in form of rippled disturbances in space time. As they circle each other, they radiate gravitational waves and their orbit shrinks.

The global team detected the neutron star collision on August 17, alerting astronomers around the world to the likely existence of signals such as light, gamma rays and radio waves from the same event.

If we can pinpoint the rate, we can determine the Universe's age, and how much matter it contains.

The featherweight masses of the objects involved - between 1.1 and 1.6 times that of the Sun - identified them as neutron stars. One teaspoon of material from a neutron star would weigh about 10 million tons.

These are small, dense stars. Spectroscopic identification of r-process nucleosynthesis in a double neutron-star merger.

Rizzo works closely with O'Shaughnessy on parameter estimation, a type of analysis that uses statistical methods to make predictions about the system that produced the gravitational waves.

"I would suggest that the Nobel Prize in physics this year wasn't given so much for the first detection of gravitational waves, but for opening up the field of gravitational astronomy", Harry said. But what does that actually mean?

Since the '50s, scientists have wondered: Where do most of the elements in the periodic table come from?

For example, observations of gravity from the collisions of high mass objects, like GW170817, are considered one of the few ways to test Einstein's theory.

Within hours, thousands of astronomers searched the sky, eventually spotting the explosive leftovers of the neutron star mashup. And somehow information about that change in gravity has to get from that object to the other objects that experience its gravity.

As a bonus, the near-simultaneous arrival of the LIGO signal and the gamma ray burst confirms that gravitational waves travel at the speed of light, as predicted by the theory of relativity, and provides a new method to determine the Hubble constant, which measures the rate of expansion of the universe.

And this happens as quickly as it possibly could.

When two neutron stars merge, it creates an explosion more powerful than 1,000 supernovae.

Like all gravitational wave discoveries to date, this one has been shrouded in secrecy.

By observing a kilonova "up close and personal" for the very first time, and seeing how well it fits into the unfolding astronomical storyboard that began with the neutron star merger, astronomers have taken a huge leap forward in our understanding of these violent cosmic events.

Another mystery solved: neutron star smashups are now known to be one source for the bright flashes of high-energy radiation known as short gamma ray bursts. "For us, that's the Holy Grail".

"I think we are converging towards a time when LIGO/Virgo alerts will become public and will be distributed within minutes", Howell says.

Jim Ulvestad, acting assistant director for mathematical and physical sciences at the National Science Foundation, said that "dozens, if not hundreds" of scientific papers have already been submitted or will soon be submitted for publication based on the observations of the event. We made a decision to drop all other plans for that evening, and went for a spectral observation with Salt, since you need a large telescope for such observations breaking up the light into all its colours.

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