1. Presented by Kesler Science
Life Cycle of a Star
Created by Kesler Science – More 5E lessons at KeslerScience.com
Presented by Kesler Science

2. Essential Questions: What is the life cycle of a star?
How does the mass of a star predict the sequence of events in the life cycle of a star?

3. Life Cycle of a Star Vocabulary
The sequence of changes that occur in a star as it ages.
Infant
Youth
Middle Age
Old Age
Death
This is a great time to talk about what a cycle is. Ask students to name all the cycles they know or have studied. The human life cycle is good for comparing to a star’s life cycle.
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4. This can be used to help students realize that stars progress through a life cycle.
Make sure they understand that star life is in millions/billions of years.
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5. Quick Action – INB Templates
Life Cycle of a Star
Cut out the Life Cycle of a Star template.
Glue it into your journal.
Have the students fill in the names of each phase as you discuss the Vocabulary.
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6. A thinly spread area of gas and dust The gas is mostly hydrogen (H2)
Life Cycle of a Star Vocabulary
Where do stars come from?
Interstellar medium
A thinly spread area of gas and dust
The gas is mostly hydrogen (H2)
The dust is mostly carbon (C) and silicon (Si) 
You might want to talk about the Big Bang here to help students understand where the gas and dust come from.
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7. Life Cycle of a Star Vocabulary
Nebula
Interstellar medium begins to collect into big clouds.
The birthplace of stars, as stars are made up of gas and dust.
“Star Nursery”
At this time talk about gravity and how it starts to pull the gas and dust together.
Every dust particle has a gravitational attraction to another dust particle.
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8. Protostar Life Cycle of a Star Vocabulary
Inside the nebula are regions of greater and less gravity causing the gas and dust to pull together.
As more atoms gather, their gravitational attraction increases.
Not a very stable phase because many reactions are occurring within the protostar.
Also talk about how these particles begin to heat up as they collide with each other.
Help the students to understand this is not a star yet, just the beginning reactions that lead up to stars. How does this relate to a human life cycle?
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9. Equilibrium Life Cycle of a Star Vocabulary
A battle between gravity and gas pressure
Reactions within life cycle phases where gravity and gas pressure are constantly changing.
Equilibrium is reached when both are equal.
This is about the reactions taking place in the protostars.
Equilibrium – How it Works
Gravity pulls gas and dust inward
The core temperature increases as gas atoms collide.
Density of core increases as more atoms are pulled into the core.
Gas pressure increases as more atoms collide.
The protostar’s gas pressure resists the collapse (gravity) of the nebula
The protostar reaches equilibrium when -
gas pressure = gravity
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10. Hydrogen (H2) begins fusing into helium (He).
Life Cycle of a Star Vocabulary
A Star is Born –
when a critical temperature in the core of the protostar is reached and nuclear fusion begins.
Hydrogen (H2) begins fusing into helium (He).
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11. Star Life Cycle of a Star Vocabulary
An extremely hot ball of gas, with hydrogen (H2) fusing into helium(He)at its core.
Spend most of their lives fusing hydrogen
When the hydrogen is used up, stars fuse helium to carbon
They are always trying to achieve equilibrium
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12. Main Sequence Life Cycle of a Star Vocabulary
Stars live out most of their lives in this phase.
Stars have achieved nuclear fusion.
Stars stays at equilibrium.
Stars radiate (shine) energy into space.
Stars in Main Sequence are constantly fighting to stay at equilibrium.
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13. Life Cycle of a Star Vocabulary
Low Mass Stars in Main Sequence
The mass of a star determines what happens to it after living most of its life in Main Sequence.
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14. Life Cycle of a Star Vocabulary
Low mass stars –
Half as massive as the Sun
Can live 80 to 100 billion years in Main Sequence.
Example - Red Dwarf
Our Sun –
A medium sized, low mass star
Spends about 10 billion years in Main Sequence.
A Main Sequence star for about billion years.
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15. Red Giant Life Cycle of a Star Vocabulary Phase after Main Sequence
Low and high mass Main Sequence stars progress to Red Giants.
Outer gas layers of the star expand
As the star uses all its fuel its core shrinks.
Red in color
High luminosity
You might want to add information about the sun changing into a red Giant here.
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16. Planetary nebula Life Cycle of a Star Vocabulary
Occurs at the end of a low mass Red Giant’s life.
The outer layers of the star are expelled.
The core is very hot and luminous.
The outer shell appears as bright colored gas clouds.
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17. White Dwarf Life Cycle of a Star Vocabulary
Forms when a low mass star runs out of fuel.
The core of a planetary nebula
Final stage in the cycle for low mass stars
Incredibly dense
Gravity is 350,000 times that of gravity on Earth.
Will change colors as it cools
Talk about a gas flame so students get the concept of heating/cooling changing the color of the flame. Blue flames very hot. Yellow/orange flames cooler.
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18. Black Dwarf Life Cycle of a Star Vocabulary
End product of a White Dwarf
The last stage of stellar evolution for low mass stars
No longer emits heat or light
No longer a star
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19. Life Cycle of a Star Vocabulary
Talk about how the sun is a medium size low mass star in Main Sequence and will follow the cycle of low mass stars through the life cycle.
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20. Quick Action – Life Cycle of a Star
______mass
_____ mass
Have the students Trace the life cycle of the Sun on this diagram. They should realize it is the left side of the diagram. Have them label Sun under Main Sequence.
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21. Quick Action – Life Cycle of a Star
Low Mass
High Mass
Main Sequence
SUN
Red Giant
Star-Forming Nebula
Have the students Trace the life cycle of the Sun on this diagram. They should realize it is the left side of the diagram. Have them label Sun under Main Sequence.
Planetary Nebula
White Dwarf
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22. Life Cycle of a Star Vocabulary
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23. Life Cycle of a Star Vocabulary
High Mass Main Sequence
The mass of a star determines what happens to it after living most of its life in Main Sequence.
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24. Life Cycle of a Star Vocabulary
High Mass stars -
10 times as massive as our Sun
Remains in Main Sequence for about 20 million years.
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25. Life Cycle of a Star Vocabulary
Red Super Giants
The same thing as a giant star only much bigger.
As a star gets older it begins to run out of fuel and expand.
Here you could refer the back to the slide on Red Giants.
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26. Supernova Life Cycle of a Star Vocabulary
Last stage of a massive star’s life
Occurs as the star runs out of nuclear fuel, some of its mass flows into its core.
Core becomes so heavy that it cannot withstand its own gravitational force.
The core collapses and results in a giant explosion.
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27. Neutron Star Life Cycle of a Star Vocabulary
The core left behind in a supernova
Very dense - 1Tsp. = 1billion tons
Gravity is 2 billion times that of the gravity on Earth.
Gravity presses the material in on itself so tightly that protons and electrons combine to make neutrons, yielding the name "neutron star”.
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28. Life Cycle of a Star Vocabulary
Black Hole
Forms when very massive stars collapse at the end of their life cycle
A large area in space with a very strong gravitational pull
Nothing can escape, even light.
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29. Quick Action – Life Cycle of a Star
Low Mass
High Mass
Main Sequence
Massive Star
SUN
Red Super Giant
Red Giant
Star-Forming Nebula
Have the students Trace the life cycle of the Sun on this diagram. They should realize it is the left side of the diagram. Have them label Sun under Main Sequence.
Neutron Star
Supernova
Planetary Nebula
White Dwarf
Black Hole
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30. Quick Action – Life Cycle of a Star
Journal Activity
In your INB write a passage that compares the human life cycle to the life cycle of a star.
Provide as much detail as possible.
This is a great exercise to get students writing and reflecting on their knowledge. Allow them to use their resources for better results
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31. Check for Understanding
__________
___________
Can you…
Describe why a star goes through a cycle?
Predict what stages a low mass star will pass through in its lifetime?
Label a blank Life Cycle of a Star diagram?
Clear up any confusion and answer questions.
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