Why is the distant-source count dipole larger than our motion predicts?
In plain words
Because the Earth moves relative to the cosmic microwave background, distant galaxies should look slightly more numerous in the direction of motion. Several catalogs show about twice the expected effect.
Precise statement
The CMB dipole implies a velocity of about $3.7e7\,\mathrm{cm/s}$, which predicts a kinematic number-count dipole (Ellis-Baldwin test) for distant sources. CatWISE2020 quasars and NVSS radio galaxies give amplitudes about twice the prediction, reported at about $5\sigma$ in joint analyses. Determine whether this signals a non-kinematic, intrinsic anisotropy incompatible with FLRW cosmology, or catalog systematics and clustering contributions.
What would settle it
Number-count dipoles from independent deep surveys (Euclid, Rubin, SKA) with characterized selection functions, consistent or inconsistent with the kinematic value.
Status in the literature
Unverified note
2025 to 2026 reanalyses including clustering and higher multipoles disagree on the significance.