Making waves in spacetime July 22, 2016 by Barbara K. Kennedy Please Register or Log in to view the hidden image! Waves on Earth's oceans move in endless rhythm along sandy beaches. Another kind of wave ripples to our planet from distant black holes in the universe. Less than four months after the historic first-ever detection of gravitational waves, scientists on a team that includes Penn State physicists and astronomers detected another gravitational wave washing over the Earth. "I would never have guessed that we would be so fortunate to have not only one, but two definitive binary black-hole detections within the first few months of observations," said Chad Hanna, an assistant professor of physics, and astronomy and astrophysics at Penn State. Read more at: http://phys.org/news/2016-07-spacetime.html#jCp extract: Hanna said, "Our experience with this new black-hole binary gives us confidence that we can detect—in near real-time with our present techniques—systems with very small amplitudes as we expect for binary neutron stars. We now have good reason to believe that the future for gravitational-wave astronomy and multimessenger astrophysics is bright." http://phys.org/news/2016-04-ligo-background-noise-due-gravity.html Abstract The LIGO detection of the gravitational wave transient GW150914, from the inspiral and merger of two black holes with masses ≳30M⊙, suggests a population of binary black holes with relatively high mass. This observation implies that the stochastic gravitational-wave background from binary black holes, created from the incoherent superposition of all the merging binaries in the Universe, could be higher than previously expected. Using the properties of GW150914, we estimate the energy density of such a background from binary black holes. In the most sensitive part of the Advanced LIGO and Advanced Virgo band for stochastic backgrounds (near 25 Hz), we predict ΩGW(f=25 Hz)=1.1+2.7−0.9×10−9 with 90% confidence. This prediction is robustly demonstrated for a variety of formation scenarios with different parameters. The differences between models are small compared to the statistical uncertainty arising from the currently poorly constrained local coalescence rate. We conclude that this background is potentially measurable by the Advanced LIGO and Advanced Virgo detectors operating at their projected final sensitivity. Read more at: http://phys.org/news/2016-04-ligo-background-noise-due-gravity.html#jCp
