A black hole rings nonlinearly: new gravitational overtones heard ⚡ экспресс
The first observational evidence is reported for quadratic quasinormal modes in the ringdown phase following a black hole merger. In the gravitational-wave signal of event GW250114, six nonlinear modes were identified, generated by quadratic interaction of the fundamental mode (2,2,0) and its first two overtones. At 5 times the mass of the final black hole after merger, the Bayesian factor in favor of their presence reaches 74. The analysis relied on theoretical calculations of signal shapes, which allowed subtracting nonlinear contributions from the numerical relativity model, and results from inspiral inference were used as a strong prior distribution for the ringdown phase. An additional check of phenomenological deviations in predicted amplitudes showed that zero amplitude is excluded at 3.0σ, and the theoretical expectation agrees with observations. This marks the first step toward observationally studying nonlinear perturbations of the event horizon.
When two black holes merge, the newborn hole rings like a bell, emitting gravitational waves. In the past, only the fundamental tone of this ringing was captured. But analysis of the GW250114 merger showed that the signal hides extra faint vibrations—nonlinear overtones. They arise when the main wave interacts with itself, much like a powerful strike makes a bell resonate with a complex chord.
The discovery was made by scientists from the LIGO–Virgo collaboration using a clever trick: they subtracted a standard model based on Einstein's theory from the signal recorded by the detectors. In the residue, quadratic modes emerged with a confidence 74 times greater than random noise. Their amplitude is thousandths of a proton's size. Such sensitivity allows us to peer into the heart of curved spacetime and test general relativity under extreme conditions.
The work builds on the contributions of Kip Thorne, Rainer Weiss, and John Archibald Wheeler. Now astronomers don't just hear the ringing of black holes—they can discern its finest overtones, meaning we can measure the masses and spins of these invisible cosmic bodies more precisely.
🎯 Each pair of black holes leaves a unique 'ring'; nonlinear overtones will not only let us weigh them but also determine which stars they were born from.
🎬 In Carl Sagan's novel 'Contact', a signal from space turned out to be a message from another civilization; today we are learning to listen to the voice of gravity itself.