Large-scale alignments from WMAP and Planck
  We revisit the alignments of the largest structures observed in the cosmic
microwave background (CMB) using the seven and nine-year WMAP and first-year
Planck data releases. The observed alignments -- the quadrupole with the
octopole and their joint alignment with the direction of our motion with
respect to the CMB (the dipole direction) and the geometry of the Solar System
(defined by the Ecliptic plane) -- are generally in good agreement with results
from the previous WMAP data releases. However, a closer look at full-sky data
on the largest scales reveals discrepancies between the earlier WMAP data
releases (three to seven-year) and the final nine-year release. There are also
discrepancies between all the WMAP data releases and the first-year Planck
release. Nevertheless, both the WMAP and Planck data confirm the alignments of
the largest observable CMB modes in the Universe. In particular, the p-values
for the mutual alignment between the quadrupole and octopole, and the alignment
of the plane defined by the two with the dipole direction, are both at the
greater than 3-sigma level for all three Planck maps studied. We also calculate
conditional statistics on the various alignments and find that it is currently
difficult to unambiguously identify a leading anomaly that causes the others or
even to distinguish correlation from causation.
