Astronomy basics > Tales of: The early cosmos: Out of the darkness

Dawn of Stars

The dawn of light, called the "cosmic renaissance," began as hydrogen collapsed into small areas, eventually reaching the point at which the effect of gravity became great enough to trigger nuclear fusion reactions and form the first stars. These first-generation stars were probably born at least 100 million years after the big bang.

Today, astronomers who study distant galaxies are beginning to probe the cosmic renaissance. Roughly a thousand galaxies have been identified whose light left them when the universe was about 1 billion years old. At that time stars were forming at a rate about 10 times higher than in the present-day universe. Stars in that early period were making heavier elements, such as carbon and oxygen, which mixed with original gas from the big bang to create successive generations of stars.

At greater distances (looking farther back in time) our view becomes murkier; the number of known galaxies is smaller and their distances are more uncertain. Using the deepest images from the largest ground- and space-based telescopes, astronomers are just now beginning to see into the era when the first stars may have formed.

Astronomy basics > Tales of: The early cosmos: Out of the darkness