Wilkinson Microwave Anisotropy Probe

The Wilkinson Microwave Anisotropy Probe (WMAP) was a NASA spacecraft that mapped tiny temperature variations in the cosmic microwave background. Its measurements constrained the universe’s age, composition, and geometry.

Differential radiometer: An instrument that measures the difference between signals received from two directions. WMAP compared two sky directions at once to suppress common instrumental and environmental signals.
ΛCDM model: The cosmological model combining a cosmological constant, cold dark matter, and ordinary matter. WMAP’s parameter measurements strongly supported this model of cosmic evolution.
Cosmic microwave background discovery: The 1965 detection of pervasive microwave radiation attributed to the hot early universe. The discovery created the observational target that WMAP was designed to map precisely.
WMAP first-year results: WMAP’s initial full-sky cosmological results, released in 2003 from its first year of observations. They delivered an early, precise estimate of the universe’s age and composition.
Planck satellite: A European Space Agency spacecraft that surveyed the cosmic microwave background from 2009 to 2013. Planck followed WMAP with more frequency channels and finer angular resolution.
Cosmic microwave background: The relic thermal radiation released when the early universe became transparent to light. This ancient radiation was the signal WMAP mapped across the sky.
Age of the universe: The elapsed time since the universe began expanding from its hot, dense early state. WMAP data yielded a precise estimate of roughly 13.7 billion years.
COBE: NASA’s Cosmic Background Explorer satellite, which measured the microwave background’s blackbody spectrum and detected its anisotropies. COBE established that background fluctuations existed; WMAP mapped them at much finer detail.
WMAP five-year results: WMAP cosmological results published in 2009 using five years of observations. The longer dataset sharpened parameter constraints and strengthened tests of inflation.
BOOMERanG experiment: A balloon-borne experiment that measured cosmic microwave background anisotropies over a limited part of the sky. Its focused balloon observations complemented WMAP’s repeated full-sky coverage.

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