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January 12, 2011

The new cosmic microwave background

Every 10 years or so, astronomers get a new view of the sky from space, measured in the microwave light frequencies. To get the best view of these wavelengths, we need to observe from space.

In the 1990s, NASA launched the COBE space telescope which took our first image of the whole sky in the microwave. Cosmologists were very excited to see that the sky "glowed" at a blackbody temperature of 2.7Kelvin. This glow is the remnant of the Big Bang.

In the 2000s, NASA's WMAP telescope also mapped the sky in the microwave wavelengths, but at a higher spatial resolution. WMAP showed that there were hot spots and cold spots in this background radiation. These fluctuations told us about the amount of matter (both normal and dark) in the Universe. However, WMAP still lacked the resolution to see real astrophysical objects in the sky.

Now it is Europe's turn. ESA (the European Space Agency) launched Planck a few years back and the first data and science was shown yesterday at the AAS meeting here in Seattle. Planck can actually see the radiation generated by the hot gas in galaxy clusters. And since Planck also has good frequency as well as spatial resolution, it can separate the clumps of gas in clusters from the hot and cold clumps seen in the WMAP data (those were not associated with real objects).

In this image below, you can see how the galaxy cluster first looks like a cold (blue) spot on the sky. But then, as we look at higher frequencies, the cluster looks hotter (red). This is how Planck is finding galaxy clusters.

Because Planck is an all sky survey, it is likely that the telescope will find the most massive galaxy clusters in the Universe.


Posted by christoq at January 12, 2011 11:27 AM


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