Planck 2013 results. XXVII. Doppler boosting of the CMB: Eppur si muove

Our velocity relative to the rest frame of the cosmic microwave background (CMB) generates a dipole temperature anisotropy on the sky which has been well measured for more than 30 years, and has an accepted amplitude of v/c = 1 x 23(-10), or v = 369 km s(-1). In addition to this signal generated by Doppler boosting of the CMB monopole, our motion also modulates and aberrates the CMB temperature fluctuations (as well as every other source of radiation at cosmological distances). This is an order 10 3 e ff ect applied to fluctuations which are already one part in roughly 105, so it is quite small. Nevertheless, it becomes detectable with the all- sky coverage, high angular resolution, and low noise levels of the Planck satellite. Here we report a first measurement of this velocity signature using the aberration and modulation e ff ects on the CMB temperature anisotropies, finding a component in the known dipole direction, (l; b) = (264 ffi; 48 ffi), of 384 km s 1 +/- 78 km s 1 (stat :) +/- 115 km s 1 (syst :). This is a significant confirmation of the expected velocity.