The IR part (colored orange) was taken by the space-based
Herschel telescope, and shows cold, cold dust. Even though this
dust is just a few degrees above absolute zero, it still emits
feebly in the infrared; the power of the telescope coupled with
the relatively small distance to the galaxy make it easier to
spot. The X-ray part of the picture (in blue) couldn't be more
different. Taken with the orbiting Chandra Observatory, it shows
the hottest, most violent objects in the galaxy: black holes
gobbling down matter, gas heated to millions of degrees by
dense, whirling neutron stars, and the high-energy radiation
from stars that have exploded, sending out vast amounts of
material that slam into surrounding gas, creating shock waves
that heat the gas tremendously, generating X-rays. I love the
color contrast in this image, the fact that we're seeing
entirely different populations of objects, and also the simple
idea that this is such a strange view of the Andromeda galaxy, a
huge spiral so bright and close it's