If you're seeing this message, it means we're having trouble loading external resources for Khan Academy.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

3. Stars & Elements
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.
All content in “3. Stars & Elements”

3.0—How Were Stars Formed?

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.

3.1—Creation of Complex Elements

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.

3.2—Way of Knowing: Stars and Elements

Aging and dying stars get hotter than… well, they get hot. Hot enough to create new, heavier elements. What's so special about the heavier elements? Imagine life without metal.

Glossary

Review Big History vocabulary and take the glossary challenge.

Other Materials

Access a range of other materials to support learning about this unit.

Resources

Download the teacher resources from the Big History Project classroom version of this course. Text transcripts for videos are also available.