LAMBDA Graphics: CMB Solar Dipole Amplitude and Direction

The microwave dipole (ℓ = 1) anisotropy is attributed to the motion of the Solar system with respect to the rest frame of the CMB, and thus Doppler shifted CMB monopole radiation. Computation of the velocity vector is complicated by the presence of Galactic emission, and results have evolved with improvements in foreground removal techniques and instrumental sensitivity.

We show direction and amplitude of the dipole as computed from five separate determinations. Uncertainties (68% C.L.) are quoted as the quadrature sum of both statistical and systematic estimates, as provided in the references. Note that the COBE uncertainties in the table are 95% C.L., but 68% C.L. are used in the plots.

Data Source	Year	Amplitude (μK)	l (deg)	b (deg)	Reference
COBE	1996	3372 ± 7	264.14 ± 0.30	48.26 ± 0.30	Fixsen et al. 1996
WMAP	2009	3355 ± 8	263.99 ± 0.14	48.26 ± 0.03	Hinshaw et al. 2009
Planck LFI+HFI	2016	3364.5 ± 2.0	264.0 ± 0.03	48.24 ± 0.02	Planck I 2016
Planck HFI	2020	3362.08 ± 0.64	264.02 ± 0.0085	48.253 ± 0.004	Planck III 2020
SRoll2.2 HFI	2021	3361.90 ± 0/36	263.959 ± 0.017	48.260 ± 0.007	Delouis et al. 2021