Phase 1: Protostar

- The earliest stage in a star's life

- The star's birth derives from a cloud of dust and gas known as the nebula (the "stellar nursery")

- During this stage, there are cold temperatures and high densities, which allow gravity to prevail thermal pressures and begin the gravitational collapse that will start the formation of the star

- The star looks like any other star, but there is no fusion taking place inside the core because of the cool temperatures

- The rotation of the protostar creates a strong magnetic field

- The protostar turns into a main sequence star once it reaches a temperature greater than 10 million K

- Occasionally... a star with a mass equivalent to .008 times or less than the mass of the Sun will never reach a temperature to allow nuclear fusion to take place.  This is called a brown dwarf

- On another occasion... a star with a mass equivalent to 200 times or greater than the mass of the Sun will create too much internal pressure, which in response, overwhelms the star and leads to an emission of it's outer layer elements.

Phase 2: Main-Sequence Stage

- At this point, the star has reached an extremely hot temperature

- With this high temperature present in the core, the stars able to begin the process of nuclear fusion

- Hydrogen fuses into Helium --> creating energy

- Fusion continues to occur and eventually the star becomes stable

- This phase's duration depends on the star, but it varies between a numerous million or billion years

Phase 3: Red Giant

- After the main-sequence star uses all of it's hydrogen (**energy**), the outer layers of the star expand

- The star turns into a very large star known as a Red Giant

- Because of its great size, the luminosity of the star is much stronger/brighter

- The star has a much cooler surface temperature

- They have diameters roughly between 10 and 100 that of the Sun

- During this phase, the helium fuses into carbon within the star's core

- Eventually, the star can no longer take the stress from the fusion and will expel it's outer layers into space

Phase 4: White Dwarf

- The core that is left behind from the emitted outer layers of the Red Giant is known as a White Dwarf

- The emitted outer layers for a cloud of debris which is known as the Planetary Nebula

- The White Dwarf is extremely dense.  One teaspoon amount of a white dwarf is equivalent to 5 tons!

- White dwarfs are extremely dense due to the gravitational force

- The stellar core eventually cools so much that the star can no longer be seen (aka black dwarf)

- If a white dwarf has a mass eight times or greater than the Sun, the dwarf will fuse with many different elements until it creates iron

- Iron cannot start up the fusion process because of the differences between its needed input and output of energy

- In response to this disadvantage of iron, the dwarf's core (which is the entire body itself) collapses and explodes

Phase 5: Supernova

- The explosion of the White Dwarf is knows as the Supernova

- This explosion allows the release of all energy inside the core/dwarf

- The explosion is around 100 million times brighter than the sun and lasts only

- Supernovas are supposedly where all elements heavier than hydrogen and helium came from

There are two types of supernova:

1) occurs in a binary star system - one star's gas falls onto a white dwarf, causing it to explode into a supernova

2) Occur in the stars 8 or more times massive than the sun - malfunctions with the dwarf's elements lead to a collapse of the star, causing it to explode into a supernova

Phase 6: Neutron Star

- At the center of the Supernova is a small cluster of neurons known as a Neutron Star

- The neutron star is very, very dense

- It is created from the explosion, which caused protons and neutrons to combine; thus, creating a neutron star

Phase 7: Black Hole

- If the mass of a neutron star, it is possible the star can collapse further into space and create what is known as a Black Hole

- The gravitational pull that takes place in a black hole is so strong that nothing can escape it

- They are so strong that they mutate the space around it and can even suck other matters into the hole!


- The class notes

- "The Life Cycle Of A Star." The Life Cycle Of A Star. N.p., n.d. Web. 13 Oct. 2014.

- "Life Cycle of Stars." Life Cycle of Stars. N.p., n.d. Web. 16 Oct. 2014.