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Scientists detect gravitational waves from 4 new black-hole collisions



Astronomers have now made more gravitational wave observations than they can count on their fingers.

LIGO and Virgo gravitational-wave observatories scientists report four new groups of these waves in space-time. These additions bring the total to 11, the researchers say in a study published on December 3 on arXiv.org. This represents a major advance since the first gravitational wave detection in 2015 ( SN: 3/5/16, p. 6 ).

All but one of the eleven wave groups were whirled up in violent clashes of two black holes. Instead, the detection reported in October 2017 came from the collapse of two star bodies, the so-called neutron stars ( SN: 11/11/17, p. 6 ).

The observations begin to reveal how often such waves shake the cosmos and the properties of the shadowy cosmic figures that unleash the waves. For example, the data suggest that black holes were clustered earlier in the history of the universe, the researchers report in a second study published on December 3 on arXiv.org. The team also concluded that few fusions contain black holes that are more than 50 times the mass of the Sun.

"There is clear evidence that these black holes [larger] are missing," says LIGO member Daniel Holz, astrophysicist at the University of Chicago. Some theoretical physicists had predicted such a lack of bulky black holes based on the physics of the stellar explosions that create the cosmic abysses.

Record breaking black holes led to a new set of spacetime trembling. The total mass of the colliding colossi was the largest yet discovered, with one black hole accounting for about 50 times the mass of the sun and the other 34 times the solar mass. These waves were also farther away than any previous discovery: about 9 billion light-years from Earth or give billions. "It is striking in every way," says physicist Emanuele Berti of Johns Hopkins University, who was not involved in the research. "This is super interesting."

The two LIGO detectors ̵

1; in Hanford, Washington, and Livingston, La, – and Virgo near Pisa, Italy, are closed for upgrades until next spring. Improvements in equipment could triple the number of sightings of gravitational waves, says Holz. "We will get a whole lot more."


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