stellar evolution

• protostar is when parts of the nebula begin to collapse and become denser. the clumps will heat up but is still not a star until nuclear fusion begins in its core
• the main sequence is after the protostar. It is where stars spend most of its life and it happens when the star gets hot enough for nuclear fusion to happen. this is where they fuse hydrogen into helium. they leave this stage once they run out of hydrogen fuel. High mass stars use up their hydrogen faster then low mass stars
• red giant is what happens next for low-mass stars when they run out of hydrogen fuel. the star shrinks until the center is hot enough to fuse helium into carbon. the star then grows 10x bigger and turns red
• red supergiant is the same as red giants but for bigger stars. the core is so hot and dense that it can fuse elements up to iron
• planetary nebula is when the outer layers of the stars get puffed away from the core. The leftover eventually becomes a white dwarf
• a white dwarf occurs when gravity condenses the leftover core until it is the size of the earth. They have no more energy source and slowly cool down.
• a supernova happens when a red supergiant's nuclear fusion fuses up to iron in its core. because there is no pressure to balance gravity, the star collapses and explodes. This creates all elements heavier than iron
• neutron star is formed after a supernova explosion. The core collapses under its own weight and electrons are forced into protons creating neutrons. this results in a 6 mil object with high density that spins and shoot energy into space
• a black hole only forms when the most massive stars explodes. This happens when the core of a massive star collapses on itself and has such a strong gravitational pull that nothing escapes.
• matter from exploded stars and planetary nebulas gets reused in the universe. new stars that form in areas with a lot of stardust have a higher chance of planets forming around them
• nebula is a giant cloud made out of gas and dust. it is made mostly of hydrogen and helium but could have heavier stuff if recycled stardust is in the area
• nuclear fusion is when two or more atoms slam together to make a heavier element. This gives of light and heat.
• stars must constantly be balancing the force of gravity from the mass of the star, and the pressure from nuclear fusion. if one overpowers the other, the star dies.