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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

CMB Solar Dipole Amplitude


CMB Solar Dipole Direction

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