Motion relative to an isotropic <radiation field> produces a dipole: one broad hot hemisphere and an opposite cool hemisphere. To first order $T(\theta)=T_0[1+(v/c)\cos\theta]$, where $\theta=0$ is the forward direction. This is not a narrow Galactic-plane feature and is not the intrinsic small-scale CMB pattern.

Solution

Past exam of the short options paper shared by Prelims and Parts A and B of the physics course of the University of Oxford / 2016 / S2 / 3 / b / Solution

 Solution (source code)