1. Astronomy Lesson 5 – Stars

3. Stars
All stars begin their lives as a nebula, which are huge clouds of dust and gases, mainly hydrogen and helium.
The dust and gases swirl around breaking into clumps and contracting because of gravitational forces. As the clumps bump into each other and get bigger their gravitational pull gets stronger and they attract more particles.
Eventually the clumps get dense enough and hot enough for nuclear fusion to take place where hydrogen’s (H) combine to form helium (He)

4. Star – Life Cycle
Stars give off huge amounts of energy and to do so they need fuel (hydrogen)
Eventually that fuel runs out and the star becomes either a Brown, Red or White Dwarf, A Neutron Star or a Black hole
What the Star becomes depends on its initial mass

5. Low-Mass Stars
Brown and Red Dwarfs – less mass than our Sun (between 8-40% our Sun’s mass)
Use fuel slowly - Last for 100 Billion years
Nothing spectacular about these guys!

7. Intermediate-Mass Stars
Like our Sun (40-800% it’s mass)
Last about 10 Billion years
Core collapses when hydrogen is used up which causes their outer layer to expand
Called a Red Giant or Red Supergiant
Our Sun will become one in about 5 billion years and its outer diameter will extend to Mars
Eventually outer layers disappear and it becomes a White Dwarf

9. High-Mass Stars 8-25 X larger than our Sun
Crab Supernova explosion video
8-25 X larger than our Sun
Consume their fuel very fast – die more quickly and more violently
Star expands into a Supergiant which causes the core to collapse and the outer portion to explode creating a Supernova then a Neutron Star

11. Black Holes
Can occur with stars whose masses are more than X 25 of our Sun
The remains of the supernova explosion is so large that nothing can escape due to its immense gravitational force (even light)

13. Black Holes Concluded
We cannot “see” a Black Hole, we can only detect the gravitational effects created by one
Their gravity is so strong that they can swallow up surrounding planets and stars
Like a whirlpool

14. Life Cycle of a Star

15. The Life Cycle of Stars Overview
Worksheet
Life Cycle of Stars Video

16. Scientists have discovered that the temperature of a star can be estimated by its color and brightness. **Luminosity = Stars brightness

17. H-R Diagrams
Stars can be arranged based on their luminosity (absolute magnitude) and temperature (spectral type) using a Hertzsprung-Russell (H-R) diagram
H-R Diagram Gizmo