The calm surface of a lake suddenly ripples — somewhere in the depths, an underwater cliff has collapsed. The water trembles almost imperceptibly, and the circles spread wider and wider until they reach a bobber near the shore. Similarly, a massive star, having exhausted its nuclear fuel, collapses inward: its core compresses into a superdense sphere, and the shock wave rebounding from it blows the outer layers into space. This is a core-collapse supernova. And just as a falling cliff disturbs the water, the death of a star creates ripples in the very fabric of space — gravitational waves.
Today, such waves are captured by giant laser facilities like LIGO, but they are tuned to mergers of black holes and neutron stars. Signals from core collapse are much weaker and shorter — hard to pick out from the noise. However, the next generation of detectors, especially the Einstein Telescope (ET), promises to change the game. The authors calculated how far ET could hear such an 'echo,' using simulations of explosions and maps of stellar populations. For a typical star of 15 solar masses, the detector would confidently catch a signal from up to 100 kiloparsecs away — about three times the diameter of our Milky Way. Any such explosion in our Galaxy would not go unnoticed.
Moreover, if the Einstein Telescope is combined with other future detectors, the listening horizon extends to 170 kiloparsecs. This covers not only the entire Milky Way but also its satellites — the Large and Small Magellanic Clouds. Stars are born and die there too, so the chances of catching a signal become quite real. The scientists estimated the expected event rate: several explosions per decade would leave a clear trace in the data.
The ripples on the lake fade quickly, but if you place sensors all around the shore, you can reconstruct where exactly the stone fell and how heavy it was. The same goes for gravitational waves: the shape of the signal reveals the mass of the dead star, how fast its core was spinning, and the explosion mechanism. This gives astrophysicists a new tool — not just a telescope, but a true 'stethoscope' for listening to stellar catastrophes across the Galaxy and beyond.
as written by the authors arXiv:2608.07391v1
Core-collapse supernovae are key drivers of galaxy evolution and promising sources of gravitational waves, which provide a unique probe of the physics driving their explosion mechanism. Third-generation detectors, such as the Einstein Telescope, will dramatically improve the prospects for detecting these signals. This study assesses the capability of the Einstein Telescope, alone and in synergy with next-generation detectors such as Cosmic Explorer, to detect gravitational waves from core-collapse supernovae. We estimate the detection horizons and expected event rates for sources in the Milky Way and nearby satellite galaxies. We employed the GWFish simulation framework, customized to include core-collapse supernovae waveform catalogs from state-of-the-art 3D simulations and stellar population data generated with TRILEGAL. This approach allows us to model gravitational waves detectability as a function of progenitor mass, source position and detector network configuration. Our analysis shows that the Einstein Telescope can detect gravitational waves from PNS-driven core-collapse supernovae up to distances ranging from ~20 to more than 100 kpc with a 90% confidence level, depending on the progenitor mass and waveform, while a combination of this detector in a network can extend the reach up to ~170 kpc in the most favorable cases. For a representative 15 M_sun progenitor, ET (in its 2L configuration) achieves a detection horizon of ~100 kpc, ensuring essentially complete coverage of the Milky Way and partial coverage of the Magellanic Clouds.
The energy carried away by gravitational waves during core collapse is comparable to the energy the Sun will emit over its entire lifetime — about 10 billion years.
In Arthur C. Clarke's novel 'The Fountains of Paradise,' engineers build a space elevator using super-strong materials. Such an elevator could deliver gravitational wave detectors far beyond Earth, shielding them from seismic noise.