Image:COBE cmb fluctuations.gif

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"Cosmic microwave background temperature data were extracted from the released FITS files and then combined into two linear combinations. The first is a weighted sum of the 53 and 90 GHz channels which gives the highest signal-to-noise ratio for cosmic temperature variations but includes the Milky Way Galaxy as well. In the second linear combination, a multiple of the 31 GHz map is subtracted from a weighted sum of the 53 plus 90 GHz channels to give a "reduced map" that gives zero response to the observed Galaxy, zero response to free-free emission, but full response to variations in the cosmic temperature. 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 following image just shows the reduced map (i.e., both the dipole and Galactic emission subtracted). 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."

taken from: [1]

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