Illustration of a swiftly rotating brown dwarfNASA/JPL-Caltech
Dark matter-fuelled brown dwarfs could be lurking at the centres of galaxies. If astronomers manage to spot them, they could teach us about how dark matter interacts with regular matter.

Brown dwarfs are vast balls of gas, between 13 and 72 times as massive as Jupiter but smaller than stars and with too little matter to sustain the nuclear fusion of hydrogen in their cores. The threshold at which they start fusing hydrogen and become stars, known…