Following an upgrade that took 5 years, an instrument that will look for tiny ripples in the fabric of space-time is back online and conducting searches, scientists say.
Two facilities in Louisiana and Washington that together make up the Laser Interferometer Gravitational-Wave Observatory (LIGO) have resumed the search for gravitational waves generated by the interactions of huge masses in the cosmos such as black holes and supernovae.
Gravitational waves carrying energy from these extreme events are believed to propagate through space-time like ripples in a pond spreading out from a thrown stone.
In its first run from 2002 to 2010, LIGO failed to detect such waves, but it is hoped a 5-year, $200 million upgrade will make the detector more sensitive, researchers say.
"It is deeply satisfying to realize that the hard work of so many talented scientists and engineers has finally come to fruition after two decades of concerted effort," said LIGO Laboratory Chief Engineer Dennis Coyne. "I hope that nature rewards us!"
The signal of a gravitational wave will be extremely subtle, the researchers note, but expressed confidence the new Advanced LIGO will be up to the task.
"We are there; we are in the ball park now," says theoretical physicist Kip Thorne, one of the early driving forces behind the experiment. "It's clear that this is going to be pulled off."
Researchers said the Advanced LIGO, with its upgrades, is three times as sensitive as the original detector.
While the original could only reach 65 million light years out into the universe in its search for gravitation waves, the new detector will be able to extend that search to 225 million light years away, the researchers say.
Einstein's theory of general relativity predicted gravitational waves, and while astrophysicists have seen evidence of their existence in indirect observations of their effects, a direct observation of gravity waves in our local region of space has so far eluded scientists.
"Experimental attempts to find gravitational waves have been on going for over 50 years, and they haven't yet been found," says David Reitze, the executive director of the LIGO program at Caltech. "They're both very rare and possess signal amplitudes that are exquisitely tiny."
The LIGO team involves scientists at Caltech in California, at MIT, and at the two observatory sites in Louisiana and Washington.
If the newly upgraded LIGO succeeds in detecting gravity waves, it will be an historic moment in astrophysics, the researchers say.
"The first detections will be quite dramatic for us," says MIT physicist and LIGO co-founder Rainer Weiss. "The first thing we will need to sort out is whether we truly believe what we are seeing."
