Why do distant quasar jets glow brighter in X-rays than radio waves?

Using 3D simulations of relativistic jets from distant quasars, researchers isolated how the evolving cosmic microwave background (CMB) affects radio and X-ray emission. Inverse Compton scattering—where high-energy particles collide with CMB photons—drives a dramatic X-ray brightening at high redshift that matches observations. The work predicts radio emission stays relatively constant while X-rays strengthen with distance, and reveals that slower jets show stronger evolutionary effects than faster ones.