February 11, 2003

Wilkinson Microwave Anisotropy Probe

NASA releases WMAP's first-year maps and cosmological results

The spacecraft got the "W" in WMAP on the same day its first results were unveiled, honouring team member David Wilkinson after his death.

11 February 2003: first-year data, and a new name

NASA released the first year of data and the first full-sky cosmic-microwave-background maps from the Microwave Anisotropy Probe on 11 February 2003. The same announcement renamed the mission the Wilkinson Microwave Anisotropy Probe, in honour of David T. Wilkinson, the Princeton cosmologist and founding science-team member who had died in 2002.

Thirteen companion papers were released alongside the data, covering the maps, foregrounds, the angular power spectrum, polarization, cosmological parameters and inflation.

Three million pixels, millionths of a degree

The basic-results paper presented full-sky microwave maps in five bands spanning 23 to 94 GHz, with calibration errors below 0.5 percent and a best angular resolution of 13 arcminutes. The maps used 3,145,728 pixels to portray temperature variations of millionths of a degree.

The parameter analysis found that a flat, cosmological-constant-dominated model fit the data, and gave a best-fit age of 13.7 ± 0.2 billion years.

Four percent atoms

NASA's public summary gave the present universe's composition as approximately 4 percent atoms, 23 percent cold dark matter and 73 percent dark energy. It also highlighted unexpectedly early star formation — first light about 200 million years after the Big Bang.

The data products reached researchers that day, but 11 February was the release and preprint-posting date. The principal peer-reviewed first-year papers appeared in the Astrophysical Journal Supplement in September 2003.

Sources

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What the sources leave uncertain

February 11 is the release, announcement and preprint-posting date. Calling it the journal-publication date is imprecise: the principal peer-reviewed papers appeared in September 2003.
NASA’s contemporary public release rounded the age uncertainty to a one-percent margin, while the scientific parameter paper reported 13.7 ± 0.2 billion years, approximately 1.5 percent.