1. Stars and Galaxies

2. Proto star
Black dwarf
Main sequence

3. Types of Galaxies 

4. Galaxies Galaxies are massive. Galaxies are held together by gravity
Galaxies contain new stars and old stars.
Galaxies are made of gas and dust

5. Irregular Undefined shape; no symmetry; no disk
Contains stars; usually rich in gas and dust
Held together by gravity
Young stars

6. Spiral Disk shaped; resembles a pinwheel with arms that spiral outward
Contains stars; rich in gas and dust
Held together by gravity
Middle aged stars

7. Elliptical
Round to flattened spheres;  Contains stars, a little cool gas and dust
Held together by gravity
Old stars

8. Stars & Nebula

9. NEBULA is a cloud of intersteallar gas and dust where stars or planets form.

10. STARS begin their “life” in a stellar nebula - large amount of gas
STARS begin their “life” in a stellar nebula - large amount of gas. Gravity is the force the holds a star together.

11. Protostar – baby star
Gravity can pull some of the gas and dust in a nebula together.
A star is born when the contracting gas and dust become so hot that nuclear fusion begins - protostar.

12. Generally speaking, there are two main life cycles for stars.
Main Sequence Stars
Generally speaking, there are two main life cycles for stars.
The factor which determines the life cycle of the star is its mass.
A star with more mass has a shorter life spans because they burn their fuel more quickly.
A star with less mass, burns slower and has a longer life
If a star is more than three solar masses when it is “born” or formed, it will spend much less time on the Main Sequence, have a much shorter life span, and “die” or end violently.
Once a star is born, it is set in a specific life cycle, and the outcome will not vary.

13. Red Giants
As average stars get larger and burn off the gas, they become Red Giants.

14. PLANETARY NEBULA
Eventually, the star expands and the outer parts (gases)  grow bigger and drift out into space as a planetary nebula (dust and gas).

15. When there is no more fuel:
The center of the star shrinks and gets hotter. This extra heat and pressure allows helium to fuse, which causes the outer part of the star to expand forming a red giant or supergiant, depending on its original mass.

16. White Dwarf
The collapsed core left when a red giant loses its outer layers is called a white dwarf.
It is made of pure carbon that glows white hot with leftover heat from the spent fuel. It will drift in space while it slowly cools.
It is the size of Earth, but very dense. A teaspoon of the material would weigh as much as an elephant.
Main sequence stars, specifically small and medium stars, become white dwarfs.
Any planets that the star would have had revolving around it, would have done one of the following:
moved to much farther orbits
been completely ejected from the system
been engulfed by the star in the expanded red giant phase
The star eventually cools and dims.

17. Black Dwarf
A black dwarf is a white dwarf star that has cooled completely and does not glow.
It will drift in space as a frozen lump of carbon. The star is considered “dead”.

18. MASSIVE STARS

19. Red Supergiant
A red supergiant glows red because its outer layers have expanded, producing the same amount of energy over a larger space. The star becomes cooler.

20. Supernova
A supernova is an explosion of a massive star at the end of its life; the star may briefly equal an entire galaxy in brightness.
At this point, the mass of the star will determine which way it continues in the life cycle.
Supernovas can be exceptionally bright. A supernova explosion on July 4, 1054 was so bright that it could be seen in broad daylight for 23 days.

21. Neutron Star or Black Hole?
After a star with a much mass becomes a super red giant, the gravity is so strong it causes the star to contract explode into a supernova.
The core left after the supernova will collapse into a neutron star. This is a star composed only of neutrons.
A neutron star is about 20 km in diameter and has the mass of about 1.4 times that of the Sun. A neutron star is so dense that one teaspoonful would weigh a billion tons. Because of its small size and high density, a neutron star possesses a surface gravity about 2 x 1011 times that of Earth and a magnetic field a million times stronger. Neutron stars can spin 100 times in a second.
Pulsars are spinning neutron stars that have jets of particles moving almost at the speed of light, streaming out above their magnetic poles. These jets produce very powerful beams of light. They were discovered in 1967.
Black Holes:
If the surviving core is greater than three solar masses, it contracts to become a black hole.
If a black hole passes through a cloud of interstellar matter, or is close to another “normal” star, the black hole can pull matter onto itself.
As the matter is pulled towards the black hole, it gains kinetic energy, heats up, and is squeezed by forces. As it gets hotter, this matter gives off radiation that can be measured. This allows astronomers to find black holes.

22. Neutron Star or Black Hole?
If the very massive stars expand and supernova (explode), the gravity of this mass is so strong that the gas is pulled inward, packing it into a smaller and smaller space. These massive stars become black holes when they die.
A neutron star is about 20 km in diameter and has the mass of about 1.4 times that of the Sun. A neutron star is so dense that one teaspoonful would weigh a billion tons. Because of its small size and high density, a neutron star possesses a surface gravity about 2 x 1011 times that of Earth and a magnetic field a million times stronger. Neutron stars can spin 100 times in a second.
Pulsars are spinning neutron stars that have jets of particles moving almost at the speed of light, streaming out above their magnetic poles. These jets produce very powerful beams of light. They were discovered in 1967.
Black Holes:
If the surviving core is greater than three solar masses, it contracts to become a black hole.
If a black hole passes through a cloud of interstellar matter, or is close to another “normal” star, the black hole can pull matter onto itself.
As the matter is pulled towards the black hole, it gains kinetic energy, heats up, and is squeezed by forces. As it gets hotter, this matter gives off radiation that can be measured. This allows astronomers to find black holes.

23. Average Star path
Black dwarf
Main sequence
Proto star

24. Massive Star path
Black dwarf
Main sequence
Proto star