Sep 27, 2017

Physicists detect waves from a black hole collision for the fourth time

Illustration: Rebecca Zisser / Axios

Physicists today reported observing waves in space and time from the collision of two black holes 1.8 billion light years away. It's the fourth time in two years these ripples formed from black hole mergers have been spotted, but this time they were able to more precisely locate where the collision took place in our universe.

Why it matters: It demonstrates that three detectors — two are nearly aligned and one is not — can be used to track these events in three dimensions. Ultimately, physicists want to combine observations from these detectors with those from optical telescopes to both "see" and "hear" events like neutron stars colliding, which could explain the origins of heavy elements, and test Einstein's general theory of relativity.

What they saw: On August 14, the Laser Interferometer Gravitational-Observatory (LIGO) detectors in Washington and Louisiana along with the Virgo detector in Italy observed waves from two black holes (one 31 times the mass of the Sun and the other 25 times the mass) combining to form one 53 times larger in mass than the Sun.

They also analyzed how the gravitational waves distorted space and time. What they saw was consistent with Einstein's prediction that they would "stretch and squeeze spacetime in the plane perpendicular to their direction of travel."

Sound smart: The sum of the two colliding black holes was three solar masses more than the black hole that formed, meaning the mass of three Suns was converted into the energy of the gravitational waves.

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