About 5 billion light-years away, in one of the universe’s most massive galaxies, astronomers have measured a black hole unlike any seen before. Nestled at the heart of the Cosmic Horseshoe galaxy, this ultramassive object tips the scales at about 36 billion times the Sun’s mass, roughly 10,000 times heavier than the Milky Way’s central black hole.⁠ ⁠ The host galaxy’s immense gravity bends light from a background galaxy into a glowing horseshoe-shaped arc, a phenomenon known as gravitational lensing. By combining this lensing effect with measurements of how fast stars zip around the galaxy’s core, nearly 400 kilometers per second, scientists obtained an unusually precise mass for a black hole so far away.⁠ ⁠ Remarkably, this monster is dormant, not actively consuming matter or blazing as a quasar. Its discovery relied solely on its gravitational influence, proving that astronomers can detect even “silent” ultramassive black holes across cosmic distances. The method opens the door to f...