page_title: Wilkinson Microwave Anisotropy Probe
section_title: Five-year data release
hierarchical_section_title: Wilkinson Microwave Anisotropy Probe / Measurements and discoveries / Five-year data release
caption_attribution_description: English: The Cosmic Microwave Background temperature fluctuations from the 5-year Wilkinson Microwave Anisotropy Probe data seen over the full sky. The average temperature is 2.725&#160;kelvins (degrees above absolute zero; absolute zero is equivalent to −273.15&#160;°C or −459&#160;°F), and the colors represent the tiny temperature fluctuations, as in a weather map. Red regions are warmer and blue regions are colder by about 0.0002&#160;degree.
context_page_description: The Wilkinson Microwave Anisotropy Probe, originally known as the Microwave Anisotropy Probe, was a spacecraft operating from 2001 to 2010 which measured temperature differences across the sky in the cosmic microwave background – the radiant heat remaining from the Big Bang. Headed by Professor Charles L. Bennett of Johns Hopkins University, the mission was developed in a joint partnership between the NASA Goddard Space Flight Center and Princeton University. The WMAP spacecraft was launched on June 30, 2001 from Florida. The WMAP mission succeeded the COBE space mission and was the second medium-class spacecraft in the NASA Explorers program. In 2003, MAP was renamed WMAP in honor of cosmologist David Todd Wilkinson, who had been a member of the mission's science team. After nine years of operations, WMAP was switched off in 2010, following the launch of the more advanced Planck spacecraft by European Space Agency in 2009.
  WMAP's measurements played a key role in establishing the current Standard Model of Cosmology: the Lambda-CDM model. The WMAP data are very well fit by a universe that is dominated by dark energy in the form of a cosmological constant.
context_section_description: The five-year WMAP data were released on February 28, 2008. The data included new evidence for the cosmic neutrino background, evidence that it took over half billion years for the first stars to reionize the universe, and new constraints on cosmic inflation.
  The improvement in the results came from both having an extra 2 years of measurements (the data set runs between midnight on August 10, 2001 to midnight of August 9, 2006), as well as using improved data processing techniques and a better characterization of the instrument, most notably of the beam shapes. They also make use of the 33 GHz observations for estimating cosmological parameters; previously only the 41 GHz and 61 GHz channels had been used.
  Improved masks were used to remove foregrounds. Improvements to the spectra were in the 3rd acoustic peak, and the polarization spectra.
  The measurements put constraints on the content of the universe at the time that the CMB was emitted; at the time 10% of the universe was made up of neutrinos, 12% of atoms, 15% of photons and 63% dark matter. The contribution of dark energy at the time was negligible. It also constrained the content of the present-day universe; 4.6% atoms, 23% dark matter and 72% dark energy.
  The WMAP five-year data was combined with measurements from Type Ia supernova (SNe) and Baryon acoustic oscillations (BAO).
  The elliptical shape of the WMAP skymap is the result of a Mollweide projection.
  The data puts limits on the value of the tensor-to-scalar ratio, r < 0.22 (95% certainty), which determines the level at which gravitational waves affect the polarization of the CMB, and also puts limits on the amount of primordial non-gaussianity. Improved constraints were put on the redshift of reionization, which is 10.9±1.4, the redshift of decoupling, 1090.88±0.72 (as well as age of universe at decoupling, 376.971+3.162
  −3.167 kyr) and the redshift of matter/radiation equality, 3253+89
  −87.
  The extragalactic source catalogue was expanded to include 390 sources, and variability was detected in the emission from Mars and Saturn.
caption: Five-year WMAP image of background cosmic radiation (2008).
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