After three years of upgrading and waiting, due in part to the coronavirus pandemic, the Laser Interferometer Gravitational-wave Observatory has officially resumed its hunt for the signatures of crashing black holes and neutron stars.
“Our LIGO teams have worked through hardship during the past two-plus years to be ready for this moment, and we are indeed ready,” Caltech physicist Albert Lazzarini, the deputy director of the LIGO Laboratory, said in a news release.
Lazzarini said the engineering tests leading up to today’s official start of Observing Run 4, or O4, have already revealed a number of candidate events that have been shared with the astronomical community.
“Most of these involve black hole binary systems, although one may include a neutron star,” he said. “The rates appear to be consistent with expectations.”
One such event, called S230518h, was detected last week. Researchers say that if they can confirm the data, the event was most likely caused by the merger of a faraway black hole and a neutron star.
The twin LIGO gravitational-wave detectors at Hanford, Wash., and Livingston, La., will be joined for O4 by the Virgo detector in Italy as well as the KAGRA observatory in Japan. Virgo is scheduled to take part in the run starting later this year. KAGRA will parallel LIGO’s observations for the next month, take a break for some upgrades, and then rejoin the run.