Colliding black holes were detected through spacetime ripples for the first time in 2015 by the Laser Interferometer Gravitational-Wave Observatory (LIGO), notes Space.com:Since then, LIGO and its partner gravitational wave detectors Virgo in Italy and KAGRA (Kamioka Gravitational Wave Detector) in Japan have detected a multitude of gravitational waves from colliding black holes, merging neutron stars, and even the odd "mixed merger" between a black hole and a neutron star... During the first three observing runs of LIGO, Virgo and KAGRA, scientists had only "heard" 90 potential gravitational wave sources. But now they've published new data from the LIGO-Virgo-KAGRA (LVK) Collaboration that includes 128 more gravitatational wave sources — some incredibly distant:[Gravitational-Wave Transient Catalog-4.0, or GWTC-4] was collected during the fourth observational run of these gravitational wave detectors, which was conducted between May 2023 and Jan. 2024... Excitingly, GWTC-4 could technically have been even larger, as around 170 other gravitational wave detections made by LIGO, Virgo and KAGRA haven't yet made their way into the catalog. One aspect of GWTC-4 that really stands out is the variety of events that created these signals. Within this catalog are gravitational waves from mergers between the heaviest black hole binaries yet, each about 130 times as massive as the sun, lopsided mergers between black holes with seriously mismatched masses, and black holes that are spinning at incredible speeds of around 40% the speed of light. In these cases, scientists think the extreme characteristics of the black holes involved in these mergers are the result of prior collisions, providing evidence of merger chains that explain how some black holes grow to masses billions of times that of the sun... GWTC-4 also includes two new mixed mergers involving black holes and neutron stars. [LVK member Daniel Williams, of the University of Glasgow in the U.K., said in their statement] "We are really pushing the edges, and are seeing things that are more massive, spinning faster, and are more astrophysically interesting and unusual." The catalog also demonstrates just how sensitive the LVK detectors have become. Some of the neutron star mergers occurred up to 1 billion light-years away, while some of the black hole mergers occurred up to 10 billion light-years away. Einstein's theory of general relativity can be tested with these detections, and "So far, the theory is passing all our tests," says LVK member Aaron Zimmerman, of the University of Texas at Austin. "But we're also learning that we have to make even more accurate predictions to keep up with all the data the universe is giving us." And LVK member Rachel Gray, a lecturer at the University of Glasgow, says "every merging black hole gives us a measurement of the Hubble constant, and by combining all of the gravitational wave sources together, we can vastly improve how accurate this measurement is." In short, says LVK member Lucy Thomas of the California Institute of Technology (Caltech), "Each new gravitational-wave detection allows us to unlock another piece of the universe's puzzle in ways we couldn't just a decade ago."Read more of this story at Slashdot.