Time Evolution of the CMB Quadrupole

Abstract

I show that the quadrupole of the Cosmic Microwave Background (CMB) evolves more rapidly than previously expected, as a result of the acceleration of the Sun towards the Galactic center. The acceleration, measured most recently by Gaia EDR3, implies a fractional change in the quadrupole of ~10^{-9} per year, an order of magnitude larger than expected from the evolution in the last scattering surface of the CMB.