The CMBR is not precisely uniform in all directions because the universe itself is not uniform. As our galaxy sweeps through the CMBR, this relative movement makes the sky look slightly hotter in the direction we are travelling. A tiny difference in CMBR temperature between two opposite directions in the sky previously suggested that the solar system has a speed of around 369 km/s. . However, few studies have investigated the irregularity in sky brightness due to radio emission from distant galaxies.
The researchers consulted 1.8 million radio sources from the US-based National Radio Astronomy Observatory VLA Survey catalogue while excluding radio signals coming from local cluster of galaxies known as the Virgo supercluster. The researchers considered what velocity would be required for an observer to detect irregularities in sky brightness matching those on Earth. They found that this velocity — the velocity of the solar system — is around four times that previously thought.
"The implication of this research is serious because any such anomaly implies anisotropy on a universal scale," says lead researcher Ashok K. Singal.
This would violate the cosmological principle, in which the isotropy of the universe is assumed for all epochs, he adds.
SOURCES: Singal, A. K. : ``Large peculiar motion of the solar system from the dipole anisotropy in sky brightness due to distant radio sources'' Astrophys. J. Lett. 742, L23 (2011)