A large disparity in cosmic reference frames determined from the sky distributions of radio sources and the microwave background radiation

Understand

The angular distribution of the Cosmic Microwave Background Radiation (CMBR) in sky shows a dipole asymmetry, ascribed to the observer's motion (peculiar velocity of the solar system!), relative to the local comoving coordinates.

• The peculiar velocity thus determined turns out to be $370$ km s$^{-1}$ in the direction RA$=168^{\circ}$, Dec$=-7^{\circ}$.
• On the other hand, a dipole asymmetry in the sky distribution of radio sources in the NRAO VLA Sky Survey (NVSS) catalog, comprising 1.8 million sources, yielded a value for the observer's velocity to be $\sim 4$ times larger than the CMBR value, though the direction turned out to be in agreement with that of the CMBR dipole.
• This large difference in observer's speeds with respect to the reference frames of NVSS radio sources and of CMBR, confirmed since by many independent groups, is rather disconcerting as the observer's motion with respect to local comoving coordinates should be independent of the technique used to determine it.