 Galactic thermal dust emission

Interstellar grains heated by starlight emit a modified blackbody spectrum, with a frequency-dependent emissivity multiplying the Planck law. This Galactic thermal dust emission rises across much of the microwave/submillimeter band and contaminates high-frequency cosmic microwave background measurements. Its strength and effective emissivity vary across the sky, so the frequency at which it exceeds cosmological anisotropy is not a universal constant.