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Astronomers say they have detected another set of gravitational waves — ripples in the fabric of space and time traveling throughout the Universe. It’s the fourth time this phenomenon has been measured by the scientists at LIGO, or the Laser Interferometer Gravitational-Wave Observatory. The same group made history by detecting the first wave signals early last year. While such detections seem to be routine now, this latest discovery is unique since it was also picked up by a separate non-LIGO observatory.

LIGO, which is funded by the National Science Foundation, has two observatories in Washington and Louisiana dedicated to measuring gravitational waves. But in Italy, there’s another European-run observatory called Virgo, which is virtually the same as the LIGO facilities. On August 14th, Virgo detected its first gravitational wave signal — along with the LIGO observatories — from a pair of black holes violently merging over a billion light-years away. All of LIGO’s previous detections have stemmed from merging black holes, too, but this is the first time a merger was seen by all three observatories at once. A paper about the latest discovery has been accepted for publication in the journal Physical Review Letters.

THE FIRST TIME A MERGER WAS SEEN BY ALL THREE OBSERVATORIES AT ONCE

Having a trio of observatories spotting gravitational waves is crucial to better understanding where the signals are coming from. With three detectors, scientists can now better pinpoint where the signal originates by timing when the wave arrives at each observatory. It’s similar to how three GPS satellites are needed to accurately locate something here on Earth. “That precision is incredibly better than it was before,” Jo van den Brand, a spokesperson for Virgo, tells The Verge. (Source)