Published: Fri, June 02, 2017
Sci-tech | By Javier West

Gravitational waves detected again, at furthest distance yet

Gravitational waves detected again, at furthest distance yet

The black holes identified in January were slightly smaller than those in the first detection, but they were much farther away, according to David Shoemaker, a research scientist at the Massachusetts Institute of Technology and spokesman for LIGO, an global collaboration involving more than a thousand researchers. But Einstein's theory says gravitational waves ought to be immune to this sort of dispersion-and this is exactly what the observations suggest, with this latest black hole merger providing the strongest confirmation so far. On these terms, the new black holes complied, at least a little bit. Black holes born in a stellar pair are thought to spin in the same direction. Gravity Spy engages thousands of "citizen scientists" in classifying these glitches, increasing the chances of success in the gravitational-wave search.

Maybe that's not as unusual as it sounds.

"Even for this new event, which is about two times farther away than our first two detections, we could not find any evidence that gravitational waves disperse as they travel in the fabric of space-time", said Alessandra Buonanno, a University of Maryland physics professor and LIGO collaborator, in a statement. The second detection was made in December 2015. The second detection was made in December 2015, and the third detection, called GW170104, was made on January 4, 2017.

LIGO-India will greatly enhance the scientific capabilities of the global network of observatories for astronomy, primarily by enabling precise pointing to the location of the gravitational wave events in the sky.

When the bowling balls finally converge, if they were black holes, they would orbit one another closely, creating gravitational waves and then merging together.

"The new event also provides new opportunities to test Einstein's theory of general relativity".

LIGO's observations are conducted by twin detectors in Louisiana and Washington.

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.

In all three discoveries, LIGO detected gravitational waves from the energetic mergers of black hole pairs. In the previous two events, the paired black holes seemed to have spins that were aligned.

Gravitational waves were first observed in September 2015 and the second detection occurred three months later. "In the latest merger, the final black hole was some 50 times the mass of our Sun". The latest observations reveal the existence of black holes in a "mass window" that would be consistent with this theory. In fact, the way that gravitational waves work is closely analogous to sound waves or water waves. "He woke us up in the middle of the night, which is what we love to do", says David Shoemaker, a physicist at the Massachusetts Institute of Technology in Cambridge and spokesperson for the LIGO Scientific Collaboration. When two black holes collide, they form an even bigger black hole-but not quite as large as you'd expect from simply adding up the masses of the two original black holes. 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). The team also used the detection to study how the individual black holes were spinning. Do they always have to form in pairs, or can they form separately and link up later in life?

Despite this tiny displacement, the scientists from the LIGO and Virgo scientific collaborations were able to demonstrate the black holes exhibited a property known as "spin". Scientists traced the ripple 3 billion light-years away, back to two ancient black holes on a collision course. Furthermore, the spin-axes of the black holes change, as visible through the colored patch on each black hole horizon, which indicates the north pole.The lower part of the movie shows the two distinct gravitational waves (called "polarizations") that the merger is emitting into the direction of the camera. After all, he said, Einstein conceived of it initially to explain why Mercury moved around the sun in a different way than Isaac Newton's theory indicated. Scientists at the AEI in Potsdam and Hannover and the Leibniz Universität Hannover have made crucial contributions in several key areas: highly accurate waveform models to detect the signal and infer astrophysical information from it, efficient data analysis methods running on powerful computer clusters, and advanced detector technology.

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