A NASA satellite launched in 2001 June to study small fluctuations in the cosmic microwave background left over from the Big Bang, in succession to the Cosmic Background Explorer. It was positioned at the L2 Lagrangian point of the Earth's orbit, 1.5 million km from Earth in the direction opposite the Sun, from where it could observe the Universe without interference from the Sun, Earth, or Moon. WMAP determined the age of the Universe to be 13.73 billion years to within 1% (0.12 billion years); found that the curvature of spacetime is within 1% of flat (Euclidean); determined that ordinary atoms (baryons) make up 4.6% of the Universe, to within 0.1%; dark matter (not made up of atoms) makes up 23.3%, to within 1.3%; and that dark energy makes up the remaining 72.1%, to within 1.5%. WMAP was named in honour of the American cosmologist David Todd Wilkinson (1935–2002). It ceased observations in 2010 August.
http://wmap.gsfc.nasa.gov/ Official mission website.
Subjects: Astronomy and Astrophysics.