The number of gravitational wave events, caused by massive collisions between black holes and neutron stars, has quadrupled In a series of new papers, researchers from the LIGO and Virgo collaborations have cataloged 39 “new” events, in addition to the 11 already detected since the LIGO and Virgo gravitational wave detectors were put into operation in 2015
Gravitational waves are ripples in space-time caused by collisions between black holes and other extreme cosmic phenomena When massive cosmic bodies merge, they release exceptional amounts of energy, causing ripple a wave of their location Eventually, this wave spreads over Earth, sounding detectors in the United States (LIGO) and Italy (Virgo) Gravitational wave detections have revolutionized the way we view the universe, helping scientists understand some of the most mystifying objects in space
The new catalog, announced on Wednesday, is known as GWTC-2 and includes 50 events in total, including black hole mergers, neutron star mergers and, potentially, hole-to-hole collisions black and a neutron star Thirty-nine events were detected between April 1 and September 30, 2019 after the LIGO and Virgo installations received a number of upgrades, increasing their sensitivity
The catalog update includes some of the most extreme cosmic collisions ever detected, including one revealed in September that created a black hole 150 times as massive as the sun – the largest to date – and a particularly unusual between a black hole and a « mysterious object » which does not seem to correspond to previous findings
But the merger has excited gravitational wave astronomers because it gives them a ton of new data with which to probe the very nature of these extreme cosmic collisions
« It’s a bit like the difference between finding a single Iguanodon bone and finding hundreds of Iguanodon fossils, » says Eric Thrane, astrophysicist at Monash University in Melbourne, Australia, and researcher in chief at OzGrav, an Australian research center studying wave gravitation
In a new preprinted paper, submitted to Astrophysical Journal Letters, the collaboration studied 47 of 50 events and analyzed the physical properties of black hole fusions
« Black holes are fascinating objects because they are very simple », says Thrane « They only have two numbers describing them: their mass and their spin »
The spin of a black hole can be determined by the gravitational wave signal This gives scientists a window into how black holes meet and fall into each other in deep space, revealing how they met
Black holes are created when huge stars collapse on themselves Sometimes two stars orbit for eons in what is called a « binary » Over time they lose their mass and eventually die, collapsing to form black holes But they keep spinning in orbit until they collide and form a much larger black hole In this case the rotation doesn’t change – it points in the same direction
On the other hand, if black holes have wandered the cosmos in dense star clusters, on their own, and then collide with each other, the theory suggests that this would disrupt their rotation « When this happens , you would expect the rotation to be pointing in different directions, ”says Thrane
Importantly, with plenty of new observations, the LIGO and Virgo collaboration sees both types of black holes
« We come to the origin of black holes, hence [and] how they come together and merge, » says Thrane
The last sighting conducted by LIGO and Virgo, O3b, took place between November 1, 2019 and March 27, 2020 before being shut down due to the coronavirus pandemic Data from this period is currently being analyzed and expand the catalog of gravitational wave events, further deepening our understanding of extreme cosmic collisions
Black hole, gravitational wave, gravity, Virgo interferometer, LIGO, astronomy
News from the world – UA – Astronomers probe origins of black holes after detection of 39 new cosmic collisions
