1. Life cycle of a Star By Kailyn and Krystal

2. Star Formation:
Stars start out within the clouds of dust throughout most of galaxies, also known as a nebula. Nebulas are made up of 97% hydrogen and 3% helium.
Inside a nebula there are different places where gravity cause the gas and dust to “clump” together. The “clumps” collect more mass because their gravitational attraction to other atoms attracts some more atoms to join the “clump”.

3. http://www. physics. hku
More on Star Formation
When the atoms are added to the center of the protostar it is called accretion. The many reactions inside a forming star causes the new protostar to become unstable. In order to be a star the protostar will need to keep equilibrium. Equilibrium is a balance between gravity pulling atoms toward the center and gas pressure pushing heat and light away.

4. Nebula
(In the picture shown)
A nebula is a cloud of dust. This is the first step of life of every star. When this cloud of dust undergoes pressure and gravity and “clumping” of particles.

5.
Protostar
A Protostar is a cloud of hot, dense gas and dust particles that is collapsing because of gravity to form a star
Depending on the mass, a protostar can last from 100,000 to 10 million years.
A protostar is surrounded by a thick blanket of dust and gas that shields visible light but allows large amounts of infrared and microwave radiation to get through.

6. The Life of a Low Mass Star
Protostar
Brown Dwarf
*OR *
Main Sequence star
A Brown Dwarf
A brown dwarf is an undeveloped star that doesn’t have enough mass to go through the nuclear fusion that makes the energy in normal stars.
A brown dwarf isn’t really a true star.
A main sequence star is a normal star, like the sun, that makes
its energy by burning hydrogen in nuclear reactions. We see
mostly main sequence stars in in the sky at night

7. 3. Red Giant
A Red Giant is a star that changes hydrogen to helium through nuclear fusion.
It weighs one half to ten times as much as our Sun.
Red Giants appear to be red (hence the name) and are very large.
Sooner or later all the hydrogen in the center changes to helium which causes the nuclear reaction to stop. Due to gravity, the center will get smaller and the outside will get hotter. The remaining hydrogen on the outside will fuse to make helium. The outer layers will then get much bigger and brighter

8. 4. Planetary Nebula
A planetary nebula is a nebula that is made up of gas and plasma. Planetary nebulas are made up of certain types of stars when they die.
Compared to a star they do
not last very long (only tens
of thousands of years)
Red Giants turn into planetary
nebulas when they die
The Cat’s Eye Nebula

9. 5.White Dwarf
A white dwarf is a star with enormous density. However, it is very faint. (That
means it doesn’t shine brightly.)
A white dwarf is the remains of a star that
has collapsed.
The sun will become a white dwarf after it has
used all its fuel.

10. 6. Black Dwarf
A black dwarf is made when a white dwarf gets too cool and can’t make large amounts of heat and light anymore.
Black dwarfs are not actually known to exist because it takes longer than the age of the universe for a white dwarf to become one.
This is what scientists think a black dwarf will look like since they don’t exist yet.

11. High Mass Star 1.) Protostar 2.) Main sequence star
(A large star)
1.) Protostar
2.) Main sequence star
(which has already been described)

12. 3. Supergiant
A supergiant is one of the largest stars in the Universe.
Their diameter can be up to 1,000 times
bigger than the sun.
This is another supergiant.
The north star (Polaris) and Betelgeuse (in Orion’s belt) are both Supergiants
 This is a massive supergiant star.

13. 4. Supernova
Supernova
A supernova is when a really big star (a supergiant) explodes.
It happens when a star runs out of enough energy to make light and heat
Supernovas us up their energy really fast because gravity presses on their center extremely hard.
Supernovas are HUGE explosions that rarely happen.
Without supernovas life on Earth would not be possible.
- This is because when the explosion happens it creates “heavy elements” and we need those elements for living things

14. 5. Neutron Star Neutron Star
A Neutron star is a very dense and small star made mostly of neutrons. A neutron star is held together by gravity. They are normally 1.4 to 5 times bigger than the sun.
 This diagram shows you how dense neutron stars really are, and what the are made of. It also tells you how many mores times the mass of the sun it has.

15. OR 5. Black Hole Black hole
The other possibility that a supernova can turn into is a black hole. A black hole has such a strong pull of gravity that even light can escape it.
Black holes are created any time there is a bunch of matter in a tiny space and without enough energy to stop gravity from making it collapse. This happens after a supernova explosion.
This is what scientists can predict a black Hole looks like

16. Hydrogen Fusion Helium Fusion
Basically, in Hydrogen Fusion, four Hydrogen nuclei (or protons) come together to make a Helium nucleus.
This process happens in our sun
Hydrogen Fusion releases a lot of energy. This energy fuels the sun
Helium Fusion is basically just a bunch of nuclear fusion reactions
In these reactions three helium nuclei are turned into carbon
Helium Fusion is also called the Triple-alpha process

17. Bibliography Bibliography