Stars Flashcards
Nebula
Stars form from large clouds of gas and dust in space fake nebula. This gas and dust are usually located in the spiral arms of the galaxy.
Life cycle
Nebula –> protostar –> main sequence star
High mass –> supergiant –> supernova –> neutron star or black hole (depending on mass)
Low/medium mass –> red giant –> planetary nebula –> white dwarf
Compressional waves
Occur in nebulas. These waves move across and squeeze together the gas and dust and trigger star birth. The “clouds” begin to shrink and increase in density.
Protostar
Formed when the temperature reached about 1 million degrees. The cloud begins warming due to the release of gravitational potential energy.
Main sequence star
Once temperatures reach about 10 million degrees, nuclear fusion occurs (H -> He + energy). A main sequence star has reached stellar equilibrium where there is a balance between the outward pressure due to the energy released in fusion as well as the inward pressure due to gravity
High mass stars
Highest temperatures (35000°C)
Shine blue/white
Live 10-100 million years
Middle mass stars
Mid temp (6000°C)
Shine yellow/white
Live around 10 billion years
Our sun is classified as a middle mass main sequence star
Low mass stars
Lowest temp (3500°C) Shine red Live longest : 100 billion - trillions of years long
Red giant
This is when the hydrogen in a star is gone and the core collapses. This heats up the core and helium begins fusing into heavier elements like carbon and oxygen.
Supergiants
Similar to red giants. These stars develop several shells of fusion which leads to heavier elements such as iron being formed in the core.
Planetary nebula
Once the helium in the core runs out the star begins to fall apart. The outer layers lift off to form a planetary nebula. A tiny white hot stellar core is left behind as a white dwarf.
Supernova
The core collapses violently when the accumulation of iron in the core eventually reaches a point where equilibrium is disturbed. The outer portion of the star explodes and produces a supernova.
Neutron star
The enormous explosion of a supernova causes protons and electrons to get packed together and form neutrons. This is known as a neutron star. Incredibly dense.
Black holes
Result of very massive stars. They have so much mass that during a supernova, gravity crushes the core to a pint of infinite density.
