Solar system peculiar motion from the Hubble diagram of quasars and
  testing the Cosmological Principle
  We determine here peculiar motion of the Solar system, first time from the
$m-z$ Hubble diagram of quasars. Observer's peculiar motion causes a systematic
shift in the $m-z$ plane between sources lying along the velocity vector and
those in the opposite direction, providing a measure of the peculiar velocity.
Accordingly, from a sample of $\sim 1.2 \times 10^5$ mid-infrared quasars with
measured spectroscopic redshifts, we arrive at a peculiar velocity $\sim 22$
times larger than that from the CMBR dipole, but direction matching within
$\sim 2\sigma$. Previous findings from number count, sky brightness or redshift
dipoles observed in samples of distant AGNs or SNe Ia too had yielded values
two to ten times larger than the CMBR value, %but this by far is the largest
value arrived at for the peculiar motion, though the direction in all cases
agreed with the CMBR dipole. Since a genuine solar peculiar velocity cannot
vary from one dataset to the other, an order of magnitude, statistically
significant, discordant dipoles, might imply that we may instead have to look
for some other cause for the genesis of these dipole, including that of the
CMBR. At the same time, a common direction for all these dipoles, determined
from completely independent surveys by different groups employing different
techniques, might indicate that these dipoles are not resulting from some
systematics in the observations or in the data analysis, but could instead
suggest a preferred direction in the Universe due to an inherent anisotropy,
which, in turn, would be against the Cosmological Principle (CP), the most
basic tenet of the modern cosmology.
