The European Space Agency just released the first all sky map taken by their Planck Orbiting Observatory and behold ! its a beauty.
Planck observes the sky from the far infrared all the way out to near radio frequencies, detecting cold gas and dust, star forming regions, with the aim of detecting the subtle and cooling glow of the background fire from the Big Bang itself. In this image, infrared is blue, and the longer wavelengths (out toward the radio part of the spectrum) are progressively more red. It shows the whole sky, which is why the image is an oval.
The line running horizontally across the image is the Milky Way galaxy itself. The galaxy is a flat disk, and we’re inside it, so it looks like a line. The wispy blue colored material in the image is the dust blown out of the milky way by the ceaseless comic activity like birth and death of stars, explosions, collisions etc. The red represents the Cosmic Microwave Background (CMB).
Let’s backtrack a little and understand what is CMB ? Cosmic Microwave Background is the leftover of the Big Bang. Its our only clue to the earliest instances of the universe. In the aftermath of the big bang the Universe was a very dense hot place where hydrogen and helium had not yet started forming galaxies. The CMB is the radiation given out by this hot piromidal plasma. Because light has a finite speed, the farther we look back into the universe the backward we go in time. Although initially hot, the Hubble Expansion of the Universe has Doppler redshifted this radiation to the microwave frequencies with an average temperature of about 3 degrees.
So what does the CMB tell us ? The CMB is the signature of the big bang. By studying the intensity distribution of the radiation we can determine the variation in the matter density in the earliest Universe. This variation is necessary for the subsequent development of galaxies. Using the CMB cosmologists can trace the history of the Universe till the moment after the big bang. It will also provide a first realistic test of Inflationary Models.