1. The Lifecycle of the Stars
By:
LadyFalcon12

2. Vocabulary Helium Fusion- a kind of nuclear fusion Nuclear Fusion-
Hydrogen Fusion-
a nucleus of Deuterium is formed from two protons with the emission of an anti-electron and a neutron.
Nuclear Fusion-
a nuclear reaction in which nuclei combine to form more massive nuclei with the simultaneous release of energy

3. How Are Stars Formed?
A star’s life is started by a cloud of gas and dust. This is called a Nebula.
A nebula is made up of hydrogen gas and plasma. This is the first stage of a star’s life.
Facts on Nebula:
The word nebula is Greek. It comes from the meaning of mist.
Nebula emit light of their own.

4. Small To Medium Mass Stars…
Like all stars small to medium stars start their lives the same way… as a nebula.
The second stage of a star is called a Protostar. (or known as a pre-star)
Protostar:
This is when gravity pulls atoms to the toward the center. If the cloud becomes dense enough, gravity will collapse the cloud upon it self.
A star can also become a Brown
Dwarf (or a small protostar)
A Brown Dwarf is a star too small
to create enough heat to start
fusion.
_life%2Fstarlife_proto.html

5. Main Sequence Stars.
The next stage in becoming a star is called A Main Sequence Star. This is when the star does gain enough mass to begin fusion. All main sequence stars fuse hydrogen.
Scientists say that most of the stars percent of stars are at this stage.
This stage is the longest stage.
Mr. W.’s Notes

6. Red Giants. The next stage is Red Giant.
This stage is caused by a small to medium main sequence star runs out of hydrogen and begins fusing helium.
Fusion:
is when multiple charged atomic nuclei join together and form a heavier.
If the star isn’t fusing then it isn’t considered a “real” star.

7. Planetary Nebula.
A Planetary Nebula is the 5th stage. Planetary Nebula: This becomes when a red giant completely stops fusing and the outer layers of the star drive away.
Lifecycle of a star notes
When the stars are at the Planetary Nebula stage they are near the end of their lives.
Facts About Planetary Nebulae:
*The name originated in the 18th century
*planetary nebulae only last a few ten thousand years.

8. White Dwarfs: White Dwarf:
The left over core of a star
Facts about White Dwarfs!!
*white dwarfs may only be the size of the earth, but it has the mass equal to half oh the sun.
*it is the 6th stage in forming a star.
Lifecycle of a star notes
*also called a degenerate dwarf
*it is a small star made up of electron-degenerate matter.
Electron-degenerate Matter:
matter which has such very high density.

9. Black Dwarfs
Black Dwarfs are white dwarfs that have cooled off over trillions of years until it no longer emits light.
*This is the last stage for Small to Medium Stars. *
These stars are usually found in the milky way.

10. The Lifecycle of High Mass Stars Are:
Formed the same way EXCEPT…
The 3rd stage, which is called a Red Supergiant.
Red Supergiant:
Massive main sequence star runs out of
Hydrogen and begins fusing helium, carbon,
Oxygen etc.
Lifecycle of a star notes
*15 solar masses *

11. Supernova!! http://en.wikipedia.org/wiki/File:Keplers_supernova.jpg
A Supernova is when fusion stops. The star collapses and creates a huge explosion.
Lifecycle of stars notes
They are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy.
It takes over several months or weeks
dust to totally clear from the galaxy.

12. Neutron Star.
A Neutron Star is a super dense core of a star left over after a supernova.
They are only 5 to 15 miles on diameter but have a mass times that of the sun.
This is the 5th stage in forming a high mass star Lifecycle of a star notes

13. The Last stage is… A Black Hole:
Stars with masses of 25x to 50x of the sin form black holes after a supernova.
The leftover core of a star is so dense that it causes the gravitational collapse.
Lifecycle of a star notes.
>Once a star (or anything for that matter) falls into the black hole it will never be able to excape its gravitational pull.
>a black hole may reveal its presence through interaction with matter orbiting the event horizon