Researchers have detected a significant signal from a black hole merger, known as GW250114, which may be related to its event horizon. The signal is described as a "fingerprint" or "signature" of the black hole's event horizon, and it is considered a first-time detection of this phenomenon. The observation is said to provide a direct window into the black hole's event horizon, although the specifics of the finding, including the nature of the signal, are still being reported in varying terms.