The Laser Interferometer Gravitational-wave Observatory is back on the hunt for ripples in spacetime, months after reporting the first signature of a black hole collision in gravitational waves.
After a series of upgrades, the LIGO detectors at Hanford in Washington state and near Livingston, La., made the transition from engineering test runs to science observations at 8 a.m. PT today.
LIGO’s first detection of gravitational waves – a phenomenon that was predicted by Albert Einstein’s theory of general relativity back in 1915 – occurred during an engineering run in September 2015. But it took until February for the LIGO team to confirm the detection and report it to the world.
Scientists determined that the faint perturbations in the fabric of spacetime were created by a smash-up involving two black holes 1.3 billion light-years away. The violent collision created one bigger black hole, but in the process, an amount of mass equivalent to three suns was converted into gravitational waves.
LIGO picked up a second, smaller pulse of gravitational waves last December. Then the detectors were shut down in January for the upgrades.
Now the Livingston detector is about 25 percent more sensitive than it was during last year’s run, and the Hanford detector has been made more powerful and more stable. Both detectors rely on sensitive lasers that sealed within an L-shaped arrangement of 2.5-mile-long tubes.
“With our improved sensitivity, and a longer observing period, we will likely observe even more black-hole mergers in the coming run and further enhance our knowledge of black hole dynamics.” Caltech’s Dave Reitze, executive director of the LIGO Laboratory, said in a news release about the resumption of observations. “We are only just now, thanks to LIGO, learning about how often events like these occur.”
The detectors could also pick up a different type of signature that’s associated with the merger of neutron stars.
“The significance of this expanding ‘window to the universe’ cannot be stressed enough, as it will illuminate the physics of merging black holes, neutron stars and other astronomical phenomena that cannot be reproduced in a laboratory setting,” France Cordova, director of the National Science Foundation, said in a statement. “The world waits with eager anticipation of what we will see and learn next, all because of the long-range vision and skills of hundreds of researchers around the world.”