1. Chapter 15 Section 3
Lives of Stars

2. How do stars begin? Nebula cloud of dust and gas in space
Nebular begins to spin and create a gravitational field
It heats up and contracts Protostar
So when does it become a star?
Gas and dust becomes very dense
Nuclear Fusion begins!

3. How long does a star live?
More Mass = Shorter Life
Burns fuel much faster!
Life span is millions of years
Less Mass = Longer Life
Burns fuel much slower!
Life span is up to 200 billion years
Example: Our Sun
Medium-mass Star
Approx. 10 billion years

4. What happens next? Medium-mass stars  Red Giant
Star begins expanding
Helium core collapses
High-mass stars  Super Giant
Star continues to expand
Heat from the core makes more nuclear fusion reactions
Both Red Giants and Super Giants are very bright, cooler than main sequence stars and unstable.

5. (Send a private message to a classmate!)
How do stars die?
Remember. . .
What is the energy source for stars?
(Send a private message to a classmate!)

6. How do stars die? A star runs out of fuel! Nuclear fusion ends
One of three outcomes:
White Dwarf
Neutron Star
Black Hole

7. Planetary Nebulas As a red giant is nearing the end of it’s life span
Parts of the star can escape and float off into space
Cat’s Eye Nebula

8. White Dwarf Blue-White Core Left over after planetary nebula escapes
Half the size of Earth
Very dense
Faint blow for billions of years

9. Supernova High-mass star Bright, hot supergiants
Runs out of fuel and suddenly explodes!
Large masses of gas and dust are flung into space.

10. Neutron Star Material left over from a supernova
Smaller, denser than white dwarfs
Size of a city
Strong Magnetic Field

11. Pulsars Spinning neutron star PULsating RAdio Sources
Emits constant beam of radiation
Can rotate up to hundreds of times per second

12. Black Holes
An object with gravity so strong that even light can’t escape it!
Created by most massive stars
Can’t be see, but only speculated

13. Create a Star Flow Chart!
Map out the life stages of a star
Use paint, whiteboards, word, or any program to draw a flow chart about the life cycle of a star.
Use images from these slides or the internet/
Make sure to include outcomes for low, medium, and high mass stars.
Briefly describe how or why the start changes states.