Stellar Life Cycle Simulation Task

Estimated Time: 45 minutes Materials: Internet-connected device, Stellar Phenomena Simulator, scratch paper.

Teacher Notes

Phenomenon: The Sun has had a steady lifespan of about 4.6 billion years, but other stars in the universe have drastically different lifespans and fates. Why does our Sun burn so steadily, and what determines how long it (and other stars) will live? NGSS Alignment (HS-ESS1-1):

• Science and Engineering Practices (SEPs): Developing and Using Models (Students use the simulation to model the relationships between mass, core temperature, fusion processes, and lifespan).
• Disciplinary Core Ideas (DCIs):
  • ESS1.A: The Universe and Its Stars (The star called the sun is changing and will burn out over a lifespan of approximately 10 billion years).
  • PS3.D: Energy in Chemical Processes and Everyday Life (Nuclear fusion processes in the center of the sun release the energy that ultimately reaches Earth as radiation).
• Crosscutting Concepts (CCCs): Scale, Proportion, and Quantity (Students observe how initial mass exponentially affects the scale of fusion and lifespan). Evidence Statements Addressed:
  1. Components: Students use the simulation to identify Hydrogen as the sun’s fuel, Helium and energy as the products of fusion, and that the sun’s lifespan is based on its initial mass (about 10 billion years).
  2. Relationships: Students observe the process of radiation and how energy is released.
  3. Connections: Students predict how Hydrogen converts to Helium, and describe the scale of energy released.

Engage

Think about the Sun. It has been shining steadily for about 4.6 billion years, providing energy for Earth. Yet, when we look at the night sky, we see stars of many different colors and brightnesses.

1. Why do you think our Sun burns so steadily? _____
2. What do you think determines how long a star will live? _____

Explore

Part 1: Stellar Nursery

1. Open the Stellar Phenomena Simulator and make sure you are on the “1. Stellar Nursery” tab.
2. The slider controls the “Protostar Initial Mass” in Solar Masses ($M_\odot$). $1.0 M_\odot$ is the mass of our Sun.
3. Test three different initial masses (including $1.0 M_\odot$) and record your observations in the table below.

Part 2: Core Fusion

1. Click on the “2. Core Fusion” tab.
2. Look at the Core Temp slider. What happens when you try to collide protons at a low temperature (e.g., 5 Million K)? _____
3. Set the Core Temp to 15 Million K (the temperature of the Sun’s core). Click “Collide Protons”.
4. What are the starting particles (fuel)? _____
5. What is the final particle produced? _____
6. What happens to the “Missing Mass”? _____

Part 3: Stellar Fate

1. Click on the “3. Stellar Fate” tab.
2. Select three different star masses and click “Fast-Forward Time »” to observe their final evolutionary stages. Record the results below.

Explain

Based on your observations in the simulation:

1. Explain the relationship between a star’s initial mass, its core temperature, and its lifespan. _____
2. Describe the process of nuclear fusion in the core of a star like our Sun. What are the inputs and outputs, and how is energy released? _____
3. Why does our Sun have a lifespan of approximately 10 billion years, while a $15 M_\odot$ star lives only a few million years? _____

Elaborate

Our Sun is currently about 4.6 billion years old. Using your data from the “Stellar Fate” tab, predict what will eventually happen to our Sun in about 5 billion years. What elements will it create at the end of its life? _____

Evaluate (Deliverable)

Construct a model (a diagram with captions) that illustrates the life cycle of a $1.0 M_\odot$ star from its birth in a stellar nursery to its final fate. Your model MUST explicitly include:

• The initial mass of the star.
• The nuclear fusion process in the core (Hydrogen fusing into Helium).
• The release of energy in the form of radiation due to “missing mass”.
• The star’s estimated lifespan.