Scientists spot rare gravity waves for the third time

Audrey Hill
June 2, 2017

Intriguingly, the observations are consistent with one of the more exotic explanations for the nature of dark matter - that dark matter haloes observed around galaxies are made up of a smattering of small black holes.

"Black holes are beautifully simple, you just need two numbers to describe them completely: a mass, how much they bend space-time, and a spin, how much space-time swirls about them", said Dr Christopher Berry, of the University of Birmingham, one of the researchers in the project.

Maybe that's not as unusual as it sounds. A second detection was announced in December 2015.

The details of the latest detection, made on January 4 this year, were published today (June 1) in the journal Physical Review Letters.

The event is significant for gravitational-wave astronomy, which scientists are developing to learn how the universe formed.

It also further affirmed Einstein's century-old description of how gravity works, including his prediction that any accelerating body with mass - a waving hand, a train leaving a station, or immensely powerful black holes mashing together in a distant corner of the universe - casts off something called gravitational waves, or faint ripples in the curvature of spacetime.

The addition of the Virgo instrument, expected to go online in August, could considerably sharpen that view-allowing, according to Cadonati, a one- to two-order-of-magnitude accuracy gain in localizing gravitational-wave sources in the sky.

The two identical observatories are L-shaped tubes with a laser running through them. Laser light is reflected by mirrors inside the arms, in an arrangement that can detect distortions in spatial dimensions to an accuracy of less than a thousandth of the width of a proton. David Ottaway, Associate Professor at the University of AdelaideThe most exciting thing about the future of gravitational waves is using detectors limited only by quantum mechanics to measure the composition of neutron stars, which are an exotic form of matter that can not be studied any other way.

This finding could favor the formation of some black holes over others. "In the latest merger, the final black hole was some 50 times the mass of our Sun". "Now this third one solidifies LIGO and LIGO's observations as the ultimate tool to see the mass spectrum of black holes in our universe". And so the missing two suns worth of energy was radiated out across the universe as gravitational waves.

According to Bangalore Sathyaprakash of the University of Cardiff in the United Kingdom, the relative orientations of the spin and orbital angular momenta of a binary black hole provide important information about how the system formed. But the black hole collision announced this week may yield yet another feather for Einstein's cap. Image Credit: Numerical-relativistic Simulation: S. Ossokine, A. Buonanno (Max Planck Institute for Gravitational Physics) and the Simulating eXtreme Spacetime project Scientific Visualization: T. Dietrich (Max Planck Institute for Gravitational Physics), R. Haas (NCSA).

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The newly reported detection also sheds light on a question about binary black holes that's been puzzling physicists. If they are formed in this manner, it's believed that the spins would be in the same direction. As pairs of black holes spiral around each other, they also spin on their own axes-like a pair of ice skaters spinning individually while also circling around each other.

In the other model, the black holes come together later in life within crowded stellar clusters. Astrophysicists have two theories: either binary black holes form separately in a dense stellar cluster, sink to the core and are paired up, or they were formed together from the collapse of two already-paired stars. In such an environment, black holes with various spins can eventually pair up in binary systems, simply through gravitational, "dynamic" attraction.

Twice past year, the groundbreaking project made headlines by reporting the detection of gravitational waves - ripples in spacetime that were predicted by Albert Einstein a century ago.

And once again, Albert Einstein's General Theory of Relativity held up.

Another line of LIGO evidence supports the idea that globular clusters play a role in the saga of dual heavy black holes.

"It looks like Einstein was right-even for this new event, which is about two times farther away than our first detection", says Laura Cadonati of Georgia Tech and the Deputy Spokesperson of the LSC. The outer contour for each represents the 90 percent confidence region.

"Normally we don't think of space as having any properties at all, so it's counterintuitive", says Michael Landry, director of LIGO's Hanford observatory.

Moving forward, LIGO should be able to detect more and more of these black hole mergers. LIGO partners with the Virgo Collaboration, a consortium including 280 additional scientists throughout Europe supported by the Centre National de la Recherche Scientifique, the Istituto Nazionale di Fisica Nucleare, and Nikhef, as well as Virgo's host institution, the European Gravitational Observatory. Detectors are being planned in India and Japan as well.

The distance to GW170104 is also twice that of LIGO's first discovery, meaning that the gravitational waves have been traveling for quite a bit longer.

Other reports by MaliBehiribAe

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