UWM researcher elusive mergers o
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For the first time, researchers have confirmed the detection of a collision between a black hole and a neutron star. In fact, the scientists detected not one but two such events occurring just 10 days apart in January 2020. The extreme events made splashes in space that sent gravitational waves rippling across at least 900 million lightyears to reach Earth. In each case, the neutron star was likely swallowed whole by its black hole partner. The discovery was made by an international team of scientists that includes 22 members of UWM’s Center for Gravitation, Cosmology and Astrophysics. Gravitational waves are disturbances in the curvature of space-time created by massive objects in motion. During the five years since the waves were first measured, a finding that led to the 2017 Nobel Prize in Physics, researchers have identified more than 50 gravitationalwave signals from the merging of pairs of black holes and of pairs of neutron stars. Both black holes and neutron stars are the corpses of massive stars, with black holes being even more massive than neutron stars. Two detections in 10 days
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In this new study, scientists announced the detection of gravitational waves from two rare events, each involving the collision of a black hole and a neutron star. The gravitational waves were detected by the National Science Foundation’s Laser Interferometer Gravitational-Wave Observatory (LIGO) and by Italy’s Virgo detector. The first merger, detected on Jan. 5, 2020, involved a black hole about 9 times the mass of our sun, or 9 solar masses, and a 1.9-solar-mass neutron star. The second merger was detected on Jan. 15, and involved a 6-solar-mass black hole and a 1.5-solar-mass neutron star. The results were published June 29 in The Astrophysical Journal Letters. Astronomers have spent decades searching for neutron stars orbiting black holes in the Milky Way galaxy, but have found none before 2020, said Jolien Creighton, UWM professor of physics who led the group in the LIGO Scientific Collaboration that found the event. “It wasn’t clear if such binaries existed at all,” Creighton said.
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Now, “we can finally begin to understand how many of these systems exist, how often they merge, and why we have not yet seen examples in the Milky Way,” said Astrid Lamberts, a researcher at Observatoire de la Côte d’Azur in France. Lamberts is a former postdoctoral researcher at UWM’s Center for Gravitation, Cosmology and Astrophysics.
