A Pinpoint Precision MAP

A pinpoint precision map of the cosmic microwave background, reported this week at a press conference by scientists associated with the orbiting Wilkinson Microwave Anisotropy Probe (WMAP), brings the early universe into sharper focus.

The credibility of WMAP's pronouncement rests on three things: its angular resolution is some 40 times better than that of its microwave predecessor, the Cosmic Background Explorer (COBE); it comprehensively surveyed the entire sky for a whole year (3 more years of data is yet to come); and it measures the polarization of the microwave radiation; the orientation of the radiation arises partly from the last scattering of light at the time of "recombination," when stable atoms formed for the first time, and partly from the time when ultraviolet radiation strewn by the first generation of stars ionized once again a lot of atoms in space.

Here are a few of the salient numbers coming out of the WMAP analysis:

• the time of recombination was 380,000 years after the big bang
• the era of the first stars was about 200 million years after the big bang (surprisingly early)
• the age of the universe is 13.7 billion years
• the accounting of matter in the universe is as follows: atomic matter makes up about 4%, dark matter about 23%, and dark energy 73%.

(For more information, see: WMAP Webpage; NASA Goddard Press Release)