StarChild Question of the Month for March 2003


When did the first stars form in the universe?

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Results from NASA's Wilkinson Microwave Anisotropy Probe (WMAP) released in February 2003 show that the first stars formed when the universe was only about 200 million years old. Observations by WMAP also revealed that the universe is currently about 13. 7 billion years old. So it was very early in the time after the Big Bang explosion that stars formed.

Observations reveal that tiny clumps of matter formed in the baby universe; to WMAP, these clumps are seen as tiny temperatures differences of less than one-millionth of a degree. Gravity then pulled in more matter from areas of lower density and the clumps grew. After about 200 million years of this clumping, there was enough matter in one place that the temperature got high enough for nuclear fusion to begin - providing the engine for stars to glow.

This result surprised many scientists who thought that it would have taken much longer for gravity to pull enough matter together to make a star.

Evolution Animation
This animation (5.0 MB) shows how the structure of the universe evolved from WMAP's "baby picture" of the universe. Matter clumps under the force of gravity, then the first stars ignite, and finally the structures of galaxies form.
(Credit: NASA/WMAP Science Team)

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