1. Chapter 30 Section 2- Stellar Evolution
“Brain Pop”
Write down two characteristics of a star that you would expect to change as that star ages.

2. Classifying stars
Classified based on temperature and brightness (H-R diagram)
Scientist use the H-R diagram to determine a star’s life cycle
Higher temperature stars are located on the left
Those stars with a higher luminosity (brightness) are located on the top
The band of temperature and brightness starting from the left top to the right bottom is called main sequence

3. Star Formation Stars begin as nebulas ( cloud of dust and gas)
Nebulas are made up of 70% hydrogen, 28% helium, and 2% heavier elements
Force of creation are due to other star’s death and the force of the explosion bringing the nebula’s particles together (gravitational pulling)
Newton’s law of gravitation: all objects in the universe attract each other due to gravitational force

4. Protostars
As the dense regions of the nebula begin to spin and shrink, a protostar is made
Protostar: disk-like flatten area of matter due to shrinking & spinning
As more matter moves into the star, heat energy is created (protostar heats up)
Around several million year later, electrons are stripped away, and move independently
Gases are then considered separate states of matter called plama
Plasma: hot ionized gas that has the same number of free moving positive ions and electrons

5. The Birth of a Star Nuclear fusion (NF) begins
when a protostar reaches
10,000,000 degrees Celsius
(18,000,032 F)
NF: process that occurs when extremely high temperatures and pressure causes less-massive nuclei to combine with more-massive nuclei
Lots of heat is released, birth of a star

6. Main Sequence 2nd longest stage
Energy is still created (in the core) due to the combining of hydrogen to helium
The more massive (heavier) a star is, the shorter amount of time is can exist in the universe
After their energy (hydrogen converted into helium or 10%) is used, they leave the main sequence

7. Leaving the Main Sequence
3rd stage
With no hydrogen as fuel, a star’s inner core will contract (be crushed) under gravity’s force
The temperature of the core increases, helium will transfer the energy into a thin shell of hydrogen
Hydrogen fusion continues and the shell (outer part) of a star expands

8. Final Destination for Sun-like stars (less massive)
When helium atoms have fused into carbon and oxygen, then a star enters its final stage..
A planetary nebula is formed due to the core’s last bit of heat expanding the gases

9. Giant & Supergiant Stars
Large red stars
Large surface area, bright
10 times larger than the sun
Once they become larger, more luminous (bright), and cooler, they leave the main sequence
Supergiant Stars
Highly luminous
On the top of the H-R diagram
100 times larger than the sun

10. Massive Stars gas energy sources

11. White Dwarfs becoming Novas and Supernovas
When planetary nebulas disperses (spreads out) matter still left starts to collapse inwardly
White Dwarf: a hot, extremely dense core of matter
Lower left of the H-R diagram and around the same size of Earth
Become dimmer= Black Dwarfs
Nova: Large explosion releasing energy and materials (happen several times)
Caused by white dwarf stars revolving around red giants and picking up gases
Supernova: Such an explosion that it blows itself apart and the red giant near it

12. Supernova

13. Final Stages of Massive stars
These stars are 8 times more massive than the sun
Can produce novas without another star’s energy
Supernovas are part of their life cycle
Carbon fuses into oxygen, magnesium, or silicon until it is made of iron
Due to lack of energy supply, star collapses inwardly and explodes

14. Neutron Stars, Pulsars, and Black Holes (Massive Stars)
Neutron Stars: Dense ball of neutrons left over after a supernova
Pulsars: Neutron stars that emit (give off) radio wave beams of light
Black holes: Crushing of a dense core

15. Section 3- Star Groups
Constellations: Pattern of stars and regions of space around each
Multiple-Star Systems: 2 or more stars closely associated
Binary stars: pairs of stars that revolve around each other (similar masses, barycenter)
Galaxy: many stars, gas, dust that bind together

16. Galaxies 4 Types
Spiral: Nucleus of bright stars and flatten spiral arms
Barred spiral: Young stars (some going through the center), gas, and dust
Elliptical: Spherical to elongated. Extremely bright in the center, have few young stars, contain little gas and dust
Irregular: no normal shape. Low mass stars, lots of dust and gas

17. Milky Way Spiral galaxy with billions of stars
It takes the sun 225 million years to orbit around the milky way galaxy

18. Quasars
Discovered in 1963
Not related to stars but to galaxies

19. Class Task-Name that GalaxyB. C. D.