Black holes can grow massive "clouds" made of light that ring like a bell when gravity waves hit them.
arXiv · March 18, 2026 · 2603.15734
The Takeaway
Through a process called superradiance, spinning black holes can pull particles out of the vacuum of space to form a 'gravitational atom.' These invisible clouds are so massive they create distinct gravitational ripples that can be detected by Earth-based observatories, revealing potentially new fundamental particles.
From the abstract
Black hole superradiance is a powerful probe of ultralight axions. If nature contains a boson with a mass of order $10^{-12}\,$eV, $\textit{mere vacuum fluctuations}$ will lead to its efficient production around spinning stellar mass black holes, forming a gravitational atom that both drains the black hole spin and decays to produce near-monochromatic gravitational waves. Existing superradiance constraints derive primarily from spin measurements of a handful of identified black holes. Here we in