Cosmic microwave background radiation temperature variations. These
maps have been smoothed with a 7 degree beam, giving an effective
angular resolution of 10 degrees. An all-sky image in Galactic
coordinates is plotted using the equal-area Mollweide projection. The
plane of the Milky Way Galaxy is horizontal across the middle of each
picture. Sagittarius is in the center of the map, Orion is to the
right and Cygnus is to the left.
The first image shows the dipole variation (and the Milky Way Galaxy).
The smooth variation between relatively hot (upper right) and
relatively cold (lower left) areas is due to the motion of the solar
system relative to distant matter in the universe. The signals
attributed to this variation are very small, only one thousandth the
brightness of the sky.
The bottom picture shows the temperature variations of the microwave
background radiation with the dipole variation and the emission from
the Milky Way Galaxy removed. The cosmic microwave background
fluctuations are extremely faint, only one part in 100,000 compared to
the 2.73 degree Kelvin average temperature of the radiation field. The
cosmic microwave background radiation is a remnant of the Big Bang and
the fluctuations are the imprint of density contrast in the early
universe. The density ripples are believed to have given rise to the
structures that populate the universe today: clusters of galaxies and
vast regions devoid of galaxies.
Courtesy COBE staellite developed by NASA's Goddard Space Flight Center
to measure the diffuse infrared and microwave radiation from the early
universe.