Monster gravitational waves spotted

Gravitational waves are back, and they’re bigger than ever. Researchers have spotted hints of space-time ripples that are light-years long, and thousands of times stronger and longer than the first gravitational waves ever found, in 2015. The first detection used the ground-based Laser Interferometer Gravitational-Wave Observatory (LIGO) detector — this time, scientists tracked changes in the distances between Earth and beacon stars called pulsars to reveal how passing gravitational waves stretch and squeeze space. The waves’ most likely source is the combined signal from many pairs of enormous black holes slowly orbiting each other in the hearts of distant galaxies.