1. Properties of Stars

2. Solar Nebula Theory Page 383 Plus handout

3. Brightness
A star can be bright because of it’s size and proximity to earth
Stars also differ in their Luminosity (how much energy a star radiates per second)

4. Temperature Determined by colour Stars vary in colour
Red 1000 oC)
Yellow (like our 6000 oC)
Blue oC)
Colour can tell us about a star’s composition by analyzing spectral patterns

5. Size and Mass Can be calculated by using luminosity and temperature
Stars vary greatly in size
Dwarf stars (0.1 the sun’s radius)
Massive stars (1000 x the sun’s radius)

6. Hertzsprung-Russell Diagram (P.376)

7. A Star’s Life Cycle
Gravity compresses a nebula and the temperature rises to oC
Fusion begins in the core (conversion of H into He)
The star “turns on”
The star’s gravity helps to keep the star from expanding due to high temperatures.
It is therefore a “stable star”
Nebula

8. Question…
What happens when the fuel runs out?

9. Answer…
It depends on the mass of the star!

10. ~The Evolution of Stars~ Low Mass Stars
Red dwarfs
Burn H slowly (100 billion years)
Eventually lose mass and turn into a white dwarf (small, hot and dim)

11. Intermediate Mass Stars –Our Sun’s Fate
Consumes H faster (10 billion years)
Once all H is used up, Helium will become the new fuel and extreme heat in core will cause expansion
Outside layers will become much cooler and it will turn into a red giant

12. A Red Giant
At this point our sun (now a red giant) will engulf the four inner planets of our solar system
Then it will most likely lose mass and turn into a white dwarf then into a very small, dense, hot and dim black dwarf star

13. Our Sun’s Fate
White dwarf
Black dwarf

14. Massive Stars
Massive stars consume Hydrogen rapidly and swell into Supergiants
Fusion stops, the star collapses and a supernova occurs

15. Supernova – Going out with a bang!
The spectacular death of a massive star
The light from the “explosion” can take a long time to reach earth which makes them difficult to spot (a needle in a haystack)

16. Spotting a supernova – A needle in a haystack

17. An illustration of a Black hole
Black Holes
After a supernova a neutron star or a black hole forms (depending on mass).
Black holes are so dense that not even light can escape them!
An illustration of a Black hole