Variability of extragalactic X-ray jets on kiloparsec scales

Super-massive black holes residing at the centres of galaxies can launch powerful radio-emitting plasma jets which reach scales of hundreds of thousands of light-years, well beyond their host galaxies. The advent of Chandra, the only X-ray observatory capable of sub-arcsecond-scale imaging, has lead to the surprising discovery of strong X-ray emission from radio jets on these scales. The origin of this X-ray emission, which appears as a second spectral component from that of the radio emission, has been debated for over two decades. The most commonly assumed mechanism is inverse Compton upscattering of the Cosmic Microwave Background (IC-CMB) by very low-energy electrons in a still highly relativistic jet. Under this mechanism no variability in the X-ray emission is expected. I will present the detection of X-ray variability in the large-scale jet population, using a novel statistical analysis of 53 jets with multiple Chandra observations, and the implications for our understanding of jet physics.