Originally posted to sci.astro.research, Feb 11, 2003, by Ted Bunn.
MAP (now WMAP -- see below) had its press conference and has released a bunch of papers on the first-year sky maps. Technical papers are at http://map.gsfc.nasa.gov/m_mm/pub_papers/firstyear.html and a pretty picture and less-technical explanation of the results is at http://map.gsfc.nasa.gov/m_mm.html
The most exciting thing about the results is that there are no big surprises! The angular power spectrum, which is the primary bit of science you get out of a microwave background sky map, is very consistent with what has become the "standard model" of cosmology: a flat inflation-based model containing dark matter and dark energy. The power spectrum is well measured past the second acoustic peak and into the third one. The temperature-polarization cross-correlation signal was also seen at about the expected level.
Although surprises in the data would have been fun, the lack of surprises is actually extremely remarkable, considering (a) how strange the "standard model" is and (b) how recently cosmology has become a mature scientific discipline.
I haven't read the papers yet -- there are 13 of them, some quite long! But here are a couple of highlights from scanning abstracts and figures:
One reason WMAP is such an improvement over previous data is that it's a single data set covering both large and small scales. To get limits on parameters from previous data, you had to stitch together COBE on large scales with other experiments on small scales. Since each experiment has its own calibration errors, that means you don't measure the heights of the peaks all that well.
That's all I'll say for now. There's a ton of information in this data set, and people will be poring over it for a long time to come, but those are the main things that jumped out at me after a quick look.
On a non-scientific note, they changed MAP to WMAP. The W stands for Wilkinson, a member of the MAP team who died last year. David Wilkinson was a leader in observational cosmology for decades, and this is a very fitting tribute to him.