What were the First Stars Like?
The first stars formed about 300 million years after the Big Bang, when the universe was still dark, out of primordial gas clouds. The first stars were made of hydrogen and helium, and no other elements — zero “metallicity.” In astrophysics, a metal is any element heavier than hydrogen or helium. The first stars were believed to be huge, hundreds of solar masses, because the chunking process of matter had just begun. The early universe was very homogeneous — there were only tiny deviations in the smooth distribution of matter. Slowly, these deviations built up, and condensed into local pockets of gas. This process took a huge amount of time because gravity is relatively weak when there isn’t already a lot of matter piled into one place. The first stars are called “Population III” stars, in contrast to the Population II stars which came after them, and Population I stars like our Sun. These later stars have much higher metal content, which influences their dynamics in important ways. To
No one is yet sure. Our Sun is not a first-generation star. It is not even second generation. The first stars to appear in the universe likely came and went about 13 billion years ago. However, deep observations by the Spitzer Space Telescope in infrared light have detected a diffuse glow, possibly from first generation stars hundreds of times more massive than our Sun. The above image shows infrared background light with bright patches that might have originated from clusters of these first objects. Gray areas depict places where nearby foreground stars from our Milky Way Galaxy were digitally removed.
