Scientists have detected for the third time gravitational waves coming from the merging of two massive black holes somewhere in the universe, the wrinkles in the fabric of space and time created by a powerful cosmic collision.
About 3-billion light-years away from Earth, the two black holes, far more massive than our sun, whirled around each other and eventually collided, generating waves like ripples in a pond. The waves spread out into the universe, expanding and contracting spacetime as they went. They reached Earth in January, where they were detected as tiny vibrations by sensitive instruments in twin observatories in Louisiana and Washington state. The collision created a single, bigger black hole, with a mass about 49 times that of the sun, the Laser Interferometer Gravitational-Wave Observatory (LIGO) announced Thursday.
LIGO first detected gravitational waves in September 2015 and publicly announced the discovery in February 2016, a century after Albert Einstein predicted their existence. The observatory announced a second detection last June, made in December 2015.
The first and second detections were located about 1.3 billion and 1.4 billion light-years away, making the third detection the farthest and earliest yet. The collision in the first detection produced a new black hole of 62 solar masses, and the second 21 solar masses. The measurements shocked scientists. Before LIGO’s first detection of gravitational waves, “all the black holes we knew about had masses less than six or seven solar masses,” said David Spergel, an astrophysicist at Princeton University and one of cosmology’s top experts. “People thought stellar evolution would have a hard time producing black holes of masses of 20 or 30 solar masses.” Suddenly, they were seeing black holes measuring 20 to 30 times the mass of the sun are colliding to make even more massive black holes—which meant massive stars exist to make them.