Ultra-high-frequency gravitational waves can transform into radio photons in interstellar magnetic fields thanks to the inverse Gertsenshtein effect. The study showed that radio telescopes like CHIME and FAST outperform many specialized detectors in searching for mergers of primordial black holes—the most likely sources of such waves. They are also sensitive to monochromatic signals from clouds of ultralight bosons around black holes. Thus, familiar radio dishes become hunters of elusive gravitational ghosts.
Gravitational waves are invisible vibrations of space itself, like the sound of a giant cosmic string. Ordinary detectors pick up the low 'notes' from the merger of large black holes. But there are also high-frequency gravitational waves — ultra-fast shudders, born from microscopic primordial black holes left over from the Big Bang. Flying through the Universe's magnetic fields, these vibrations turn into radio waves — like an acoustic guitar plugged into an amplifier suddenly sending out an electric signal. Radio telescopes like CHIME and FAST catch this signal, allowing us to hear the previously unheard. But most unexpectedly, clouds of invisible ultralight particles swarming around black holes can emit similar waves. If we catch their monochromatic 'ring,' it could be the key to unraveling dark matter — the mysterious substance that holds galaxies together.
🎯 The CHIME radio telescope, originally built to search for mysterious fast radio bursts, accidentally turned out to be an ideal gravitational wave detector.