The fourth observing run found evidence that merging black holes come in multiple types.

Scientists study ripples in space called gravitational wavesgravitational wavesRipples in spacetime caused by accelerating masses, like merging black holes.. These waves happen when massive objects crash together in deep space. A decade ago, spotting even one wave was rare. Now, giant detector networks catch them almost every day. In this paper, researchers review discoveries from their fourth observing runobserving runA period during which the detectors are active and collecting data.. They gathered huge lists of these events to study how stars live and die. Recent lists include ~100 new detections each. The detectors captured the loudest signals seen so far, along with totally unfamiliar sources. By studying the whole collection together instead of one by one, scientists found evidence for multiple subgroups of sources. This growing pool of data helps them test the rules of gravity and measure how fast the Universe expands. The team plans to release their final run catalogue in December 2026, with even bigger catalogues and louder signals coming in future runs.

Why it matters

This helps astronomers understand how stars evolve and form binaries, and it tests our theories about gravity and the Universe's expansion. For the first time, scientists can see patterns in hundreds of these cosmic events.

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