By 200 million years after the Big Bang, the Universe had become a very dark and cold place. Then things started to change. First, galaxies and nebulae formed. These were the earliest structures in the Universe. Then stars – “hot spots” of light and energy – emerged from these clouds of dust and gas. Why did they form and how did they change everything? Stars, the first complex, stable entities in the Universe, have the capacity to generate energy for millions, even billions of years. The first stars, which passed through their entire life cycles relatively quickly, produced many of the chemical elements of the periodic table. In this unit, you’ll learn how stars first formed and how the lives and deaths of stars provided the chemical diversity necessary for even more complex things.
In the years following the Big Bang, hydrogen atoms floated freely around the Universe. These atoms were slightly more packed together in some places than in others. In the more crowded areas, the hydrogen atoms were close enough to each other to let gravity do its work. In these little pockets of hydrogen, stars lit up across our Universe.
With the birth of stars, new sources of light and energy emerged all over the Universe. They burned hydrogen to create helium. Helium was used to create carbon. Neon, oxygen, silicon, and iron were also created during the lives of stars. However, once these stars started running out of fuel is when things really got interesting. It’s in the massive explosions that resulted from certain stars running out of fuel that all of the elements of the periodic table were created. Without the death of stars, our world would not exist today.