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Student Learning Goals:
Student Learning Goals:
1 To describe the features of nebulae and solar systems
2 To outline the stages in the lifecycle of a star
3 To relate the colours of stars to their age, size and distance from Earth
The universe is made up of many different features, including solar systems and nebulae. Solar systems comprise a Sun and the bodies orbiting it. Nebulae are clouds of dust and gas, often visible in the night sky, where new stars are being formed. Other nebulae contain the remains of dead or dying stars.
Nebulae
Nebulae
The word nebula means ‘a cloud or mist’ in Latin.
A nebula is a cloud of gas and dust in space. The gas is mainly hydrogen and the dust is generally as fine as smoke from a fire.
Nebulae are the birthplaces of stars.
Gravity pulls the gas together forming stars and whole solar systems.
The Orion Nebula, and other similar nebulae, have hundreds of solar systems forming within them right now.
Solar Systems
Solar Systems
A solar system consists of a central star with planets orbiting it.
It also includes the other objects found around the star, such as comets, asteroids, moons, dwarf planets and dust.
Nuclear fusion
Nuclear fusion occurs when two atoms combine (or fuse) to create a new element. Because it is so hot inside the cores of stars, hydrogen nuclei have enough energy to overcome the electrostatic repulsion between their protons. They fuse together to form helium and an enormous amount of energy is released in the process.
Figure 6.11 One step in the fusion of hydrogen happens when the isotopes deuterium (one proton and one neutron) and tritium (one proton and two neutrons) fuse together.
A neutron is released and a helium nucleus is formed (two protons and two neutrons).
Star color and temperature
When you look at stars in the night sky, you will notice that they vary in color. The color of a star is related to its temperature: blue stars are the hottest and red stars are the coolest. Stars are given a spectral class letter based on their temperature and color. As you can see in Table 6.1, our Sun is a relatively small yellow star with a surface temperature of around 6000 K, so a G-type star.
Light from stars
All stars emit a full range of wavelengths from the visible spectrum (colours). This means you would observe a complete rainbow if you were to split the star’s light into different colours using a prism. However, a star’s spectrum peaks at a certain colour, and this is the colour that we observe the star to be.
Luminosity
Stars vary in brightness, this is referred to as luminosity and is the rate at which a star produces energy. The scale of luminosity is based around our Sun, which is given a luminosity of 1.
Stars that are brighter than the Sun have a luminosity of greater than 1, and stars that are less bright than the Sun are given a luminosity of less than 1.
For example, a star with a luminosity of 100 is 100 times brighter than the Sun.
Figure 6.12 White light consists of the full range of wavelengths (colours) from the visible spectrum
FLAME TEST
FLAME TEST
Materials
Materials
7, 100 mL beakers
Wooden splints (number depends upon how many times the demo will be performed)
1 Bunsen burner
1 Striker
50 mL of 1.0M Barium Chloride (BaCl2) - Note: Barium chloride is highly toxic. Do not ingest the salt or solution.
50 mL of 1.0M Calcium Chloride (CaCl2)
50 mL of 1.0M Copper Chloride (CuCl2)
50 mL of 1.0M Lithium Chloride (LiCl)
50 mL of 1.0M Potassium Chloride (KCl)
50 mL of 1.0M Sodium Chloride (NaCl)
50 mL of 1.0M Strontium Chloride (SrCl2)
Deionized water
250 mL beaker or plastic or cardboard cup half full of water
Barium chloride is highly toxic. Do not ingest the salt or solution.
Solution Preparation:
If you need to make ≈1.0M solutions of the metallic salts follow these instructions:
Label each of the 100 mL beakers with the name of the salt that it will hold.
Add the solid metallic salts to the beakers:
12.2 grams of Barium Chloride (BaCl2*2H2O) - Note: Barium chloride is highly toxic. Do not ingest the salt or solution.
5.5 grams of Calcium Chloride (CaCl2)
8.5 grams of Copper Chloride (CuCl2*2H2O)
2.1 grams of Lithium Chloride (LiCl)
3.7 grams of Potassium Chloride (KCl)
2.9 grams of Sodium Chloride (NaCl)
7.9 grams of Strontium Chloride (SrCl2)
Add deionized water up to the 50 mL mark.
Note: if you do not have 100 mL beakers, substitute another piece of glassware and use a 50 mL graduated cylinder to add the deionized water.
Use a separate wooden splint to stir each of the solutions.
Distribute the remaining wooden splints between the solutions.
Allow the splints to sit in the solutions overnight.
Alternate options:
If you cannot find wooden splints you can substitute generic cotton swabs, or longer craft swabs.
Soak wooden splints or cotton swabs in deionized water for a few hours and then dip them into small samples of each solid before putting them through the flame.
This demonstration can easily be used as a student lab.
Star life cycle
Stars do not have a limitless fuel source. At some point, each star will run out of material to burn and will come to the end of its lifetime. The changes that stars go through in their life time are predictable and depend on their size.
A star’s life cycle is therefore dependent on its mass as well as the rate at which it is using up its fuel: we can determine this by measuring its luminosity. Generally, the more massive a star, the quicker it uses up its fuel and so the shorter its lifetime. We can also assume that the more luminous a star the shorter its lifetime.
Figure 6.13 The lIfe cycle of stars. How stars change over time depends on their size
Hertzsprung–Russell diagrams
A Hertzsprung–Russell or H–R diagram is a plot of star brightness (measured as luminosity) against star temperature/colour. In Figure 6.15, you can see a diagonal band of coloured dots that represent stars in the main sequence.
Red giants, supergiants and white dwarfs make up their own section of the graph. Remember, the luminosity scale gives us an idea of how bright a star is compared to our Sun. Stars with a luminosity of 1 are as bright as our Sun.
Figure 6.15 A Hertzsprung–Russell diagram plots star brightness (luminosity) against surface temperature.
The Sun is a yellow dwarf star, a hot ball of glowing gases at the heart of our solar system. Its gravity holds everything from the biggest planets to tiny debris in its orbit.
The Sun is composed almost entirely of hydrogen and helium gas. Multimillion-degree temperatures in its dense core sustain nuclear fusion, providing the energy source for sunlight. The surface of the Sun is marked by colossal magnetic storms. The Sun’s gravity holds in orbit a family of planets, moons, asteroids, and comets - the solar system.
Lesson Title: The Life Cycle of Stars: Understanding Nebulae and Solar Systems
Duration: 60 minutes
Grade Level: High School
Materials:
Images of nebulae, solar systems, and stars
Whiteboard or blackboard and markers
Laptops or tablets for students
Handouts or worksheets for students
Introduction (10 minutes):
Start with a hook by asking students if they have ever seen a star or a nebula.
Write down students' responses on the board.
Explain that today's lesson will focus on the life cycle of stars and the features of nebulae and solar systems.
Direct Instruction (25 minutes):
Show images of nebulae and solar systems on a projector or whiteboard.
Use the handouts or worksheets to guide students in understanding the key features of nebulae and solar systems, such as protoplanetary discs, gas clouds, and dust clouds.
Discuss the life cycle of a star, including its birth, main sequence, red giant phase, and ultimate fate.
Use the whiteboard to draw diagrams or graphs to help explain difficult concepts.
Guided Practice (15 minutes):
Have students work in pairs or small groups to research and present information about a specific stage in the life cycle of a star and how it relates to the features of nebulae and solar systems.
Encourage students to use scientific evidence to support their ideas.
Provide students with laptops or tablets to access online resources, such as scientific journals or educational videos.
Independent Practice (10 minutes):
Assign a homework task where students write a short essay on the relationship between the colours of stars and their age, size, and distance from Earth.
Encourage students to use scientific evidence to support their ideas.
Conclusion (10 minutes):
Recap the key learning points of the lesson.
Highlight the importance of understanding the life cycle of stars and the features of nebulae and solar systems.
Ask students to share their favorite thing they learned about stars and their life cycle.
Preview the next lesson and what students can expect to learn.
Activity Title: Discovering the Universe's Major Features
Duration: 30 minutes
Grade Level: High School
Materials:
Images of galaxies, stars, solar systems, and nebulae
Whiteboard or blackboard and markers
Laptops or tablets for students
Handouts or worksheets for students
Instructions:
Divide the students into groups of 4-5.
Provide each group with a laptop or tablet and access to online resources, such as scientific journals or educational videos.
Give each group a different feature of the universe to research, such as galaxies, stars, solar systems, or nebulae.
Encourage students to use scientific evidence to support their findings.
Have each group present their research to the class using images, diagrams, or graphs on the whiteboard or blackboard.
After each presentation, allow time for questions from the class and discussion.
Assessment:
Observe students' participation in group work and presentations.
Evaluate the accuracy and clarity of students' presentations.
Assign a follow-up homework task where students write a short essay on the major features contained in the universe, including galaxies, stars, solar systems, and nebulae.
Objectives:
To understand the major features contained in the universe.
To use scientific evidence to support their findings.
To develop skills in group work and presentation.
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