Cosmic Microwave Background radiation



The 3 Kelvin Cosmic Microwave Background (CMB) radiation surrounds us like a photograph of the young Universe. It's a remnant of the moment when the opaque photon-baryon plasma turned transparent and radiation (photons) decoupled from matter (baryons and dark matter particles). At that moment, when the Universe was only 300 000 years old, the photons scattered for the last time, and ever since have continued their journey unaltered towards us. The temperature of the radiation gradually decreased and is currently about 3 Kelvins -almost a perfect black body spectrum. The radiation is generated at microwave (radio) frequencies.
CMB radiation of the sky measured by COBE COBE satellite was the first to measure the cosmic microwave background radiation in a proper way in 1992. The resolution was very low and the results more or less vague.
The Wilkinson Microwave Anisotropy Probe (WMAP) has recently mapped the sky in more detail, however, still leaving many questions unanswered.

However, the CMB is not smooth but contains tiny irregularities. These anisotropies hold the key to the yet unsolved mysteries of our Universe (such as its age, the Hubble constant, and the nature of dark matter) and can help to define the conditions of its birth, and, for example, assist in studying theories of galaxy formation.

The Planck satellite, developed by the European Space Agency and scheduled for launch in February 2008, will study these tiny temperature differences more accurately than any other instrument before. To do so, the satellite must measure the whole sky. This means that it will observe all sources emitting at radio frequencies, also the ones in front of the microwave background. As a by-product we will get valuable data also of radio galaxies, interstellar gas and dust clouds, and pulsars.
Foreground radio sources must be 
separated from the CMB To get accurate CMB maps, the foreground radio sources must be separated from the CMB radiation and its tiny irregularities.

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