Life Cycle of a Star

By jitboy
  • 1 CE

    Nebula Formation

    All stars form in nebulas. The larger the mass of the nebula, the shorter the lifespan of the star that is created from it. Over time, gravity will bring the nebula together, and the hydrogen gas inside of the nebula will start spinning. and become a protostar, and once it reaches 15 million degrees, nuclear fusion will occur in the core. Then the star will begin to glow, contract slightly, and become stable. This is the main sequence. This typically lasts for millions to billions of years.
  • 2

    Red Giant

    As the main sequence star grows, hydrogen is converted into helium by nuclear fusion. When the hydrogen in the core runs out, the core becomes unstable and contracts. The mostly hydrogen outer shell of the star, starts to expand, and cools and glows red. In the core , helium fuses into carbon. The star has now become a red giant, and is cooler and larger in size than before.
  • 3

    White Dwarf - Black Dwarf

    As the helium fuses into carbon, the core collapses. Due to the core collapse, the outer layers are expelled and form a nebula. The core is now a white dwarf. Eventually, it will cool and become a black dwarf.
  • 4

    Supernova 1

    Once stars that are 5 times or more massive than our Sun reach the red giant phase, their core temperature increases as carbon is created through the fusion of helium. Gravity pulls carbon atoms together as the temperature increases, starting more nuclear fusion, forming oxygen, nitrogen, and eventually iron.
  • 5


    As the star fuses the elements into iron, the most compact and stable of all elements, it will use energy and thus the core will eventually run out of energy. Then it will experience gravitational collapse. A star around 10x the size of our Sun will undergo a supernova explosion. A star 1.3-4x the size of our Sun will become a neutron star. A star 3x the size of our Sun will become a black hole.