Insight-HXMT, China's first space X-ray astronomical satellite, has discovered a low-frequency quasi-periodic oscillation (QPO) above 200 kiloelectron volts (keV) in a black hole binary, making it the highest energy low-frequency QPO ever found. The scientists also found that the QPO originated from the precession of a relativistic jet (high-speed outward-moving plasma stream) near the event horizon of the black hole. These discoveries have important implications for resolving the long-running debate about the physical origin of low-frequency QPOs.