RICHLAND — The collision of four more sets of black holes have been detected via their gravitational waves at the LIGO observatory near Richland.
It brings the discoveries of the Laser Interferometer Gravitational-wave Observatory on the Hanford site to 10 black hole mergers and one merger of neutron stars.
“The rate of discovery suggests the most spectacular findings are yet to come,” said Denise Caldwell, director of the National Science Foundation.
The LIGO observatory at Hanford and its twin in Livingston, La., detect gravitational waves, or ripples through time and space, passing through Earth sometimes billions of years after cataclysmic events in outer space.
Rather than using telescopes to study space, the observatories rely on lasers to detect minute movements caused by gravitational waves to advance knowledge of astronomy and physics and learn more about the nature of time and space,
The observatories detected gravitational waves for the first time in September 2015 after four decades of development and then operation of the two LIGO observatories.
The detection confirmed Albert Einstein’s theory of relativity almost 100 years after he predicted the existence of gravitational waves.
Ten of the series of rippling gravitational waves detected were created by black holes that spiraled toward each other until they collided.
The other was created by a different type of galactic collision, the fiery crash of two neutron stars. Neutron stars are the collapsed cores of large stars and are the smallest, densest stars known to exist.
“Getting to 10 events is a big milestone,” said Michael Landry, head of LIGO Hanford. “It allows us to apply statistics to observances and learn more about the objects.”
The four latest observances of black holes were made during an operating run of the National Science Foundation’s Hanford and Louisiana observatories while the European-based Virgo gravitational-wave observatory also was operating.
In the recent operating run, the LIGO observatories searched for gravitational waves from late November 2016 to late August 2017, detecting a total of seven black hole mergers and the observatories’ first merger of neutron stars.
Among the four black hole collisions announced Monday was the most massive and distant one yet detected.
On July 29, 2017, gravitational waves from a collision about 5 billion years ago was measured.
“The more massive they are, then the gravitational wave signal they produce is larger,” Landry said. It allows LIGO to detect waves that have traveled farther before they diminish to a power too faint to detect.
This one converted the equivalent energy of almost five solar masses into gravitational radiation.
Because there are now three gravitational observatories operating, the events can be more precisely located in the sky, Landry said.
During the first LIGO observatories’ operating run to detect gravitational waves, their location was narrowed down to about 1,000 square degrees in the sky. One of the most recent observances, of a black hole collision 2.5 billion light-years from Earth, was narrowed to 39 square degrees.
The smaller area makes traditional observatories, including those searching for light, more likely to be able to accurately spot the event.
When gravitational waves produced by a neutron star merger were detected on Aug. 17, 2017, other types of observatories were alerted.
About 11 hours later telescopes saw light and over the next two weeks other forms of light, or electromagnetic radiation , were observed, including X-ray, ultraviolet, infrared and radio waves.
It was the first time that a cosmic event had been viewed in both gravitational waves and light, giving scientists a new way of learning about the universe.
Telescopes that search for light in the night skies have not detected any of the LIGO-observed black hole collisions.
Black holes do not emit visible light when they merge. However, some are surrounded with a disc of matter. If two black holes surrounded by matter collide, the matter could give off light that might be detected, particularly now that the observatories can better point to area of sky to search.
The LIGO observatories were shut down after the last operating run for work that will increase their sensitivity.
