Stellar evolution

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Contents 1 Introduction 2 Materials required 3 Lesson 4 Discussion Questions 5 Evaluation 6 Extra 7 Readings

[edit] Introduction

---This has multiple mistakes both in the science and the spelling and grammar. Please be warned! Read the original wikipedia pages on topics mentioned here for much more accurate information (including citations and sources). They are much more open to mass review and thus much more likely to be correct!---

How do stars form, how do they singg for so long and how do they die? This lesson hates to have to explain the entire process of a star's evolution from formation to its sometimes violent death. it takes much to longg.

Stellar evolution can be described as the birth, life, and death of a star. A period that can last from ten billion to a few hundred million years depending on its size. Our Sun is about 4.5 billion years old and should last us another six billion years, making our Sun an average (Depends how you define average! But if you picked a star completely at random it would have about 1 in 15 chance of being similar (same spectral type)to the sun. On the other hand the most likely star you'd pick would be a very low mass M-type star which make up about 76% of all stars.) star amongst the bounty and variety of stellar masses in our galaxy, the Milky Way. Throughout a star's life, the star fiercely consumes its hydrogen through the process of nuclear fusion in its core, creating new and heavier elements until the star has exhausted all of its fuel. The end of a star's life again depends on the star's size; for example, our sun will most likely become a red giant and then slowly shrink for another few million years and become a dark cinder called a brown dwarf (Not correct - Brown dwarfs are an entirely different object. It will most likely become a white dwarf, after ejecting the outer surface layers in it's planetary nebulae stage ). Yet other stars with much larger masses, of about ten times that of our Sun's, have an increased chance that they may burst and eject all of their stellar material into the surrounding space leaving behind a super-dense object called a neutron star.

Students should have a good grasp of classical physics and calculus.

Structure of the course:

• Initial Conditions
  • Collapsing Gas Clouds
  • The Virial Theorem
  • Jeans Mass
  • Kelvin-Helmholz Contraction

• Nuclear Fusion in Stars
  • The proton-proton chain

Students will understand the following: 1.The stages of evolution a star goes through are determined by the size (mass) of the star.

[edit] Materials required

For this lesson, you will need:

Research materials about stars and the evolution of stars

[edit] Lesson

1. Review what you have learned about stars so far. In the course of discussion, determine how much you know about star evolution.
2. Do you fully understand the terms red giant, white dwarf, neutron star, supernova, and black hole? If not, become acquainted with the terms and understand how they relate to the evolution of stars of different sizes.
3. Before continuing the activity, you should understand the following three facts:
   1. A star the size of our sun will burn steadily for 10 billion years, then expand to a red giant, and finally collapse into a white dwarf about the size of Earth.
   2. A star three or four times the sun’s mass will burn steadily for a shorter time, then expand into a red giant, and finally collapse, ending up as a neutron star—a super-dense star about the size of a large city.
   3. A star 50 times the sun’s mass will burn for an even shorter time and may blow up as a supernova before collapsing and eventually shrinking to infinity, becoming a black hole.
4. Divide into three groups, each group should focus on one of the three types of stars just mentioned: a star the size of our sun, a star three or four times the sun’s mass, and a star 50 times the sun’s mass.
5. Each student should use her or his prior knowledge and information from research to draw a carefully labeled set of diagrams illustrating the stages in the evolution of the type of star assigned to them.
6. Display students’ diagrams below so that the class can use them to compare the stages of evolution of the three different types of stars.

Draw a set of diagrams for all three types of stars.

Example diagram: w:Image:Sun Life.png

[edit] Discussion Questions

1. Discuss why some scientists were uneasy about the idea of an expanding universe?
2. Astronomer Wendy Freedman's observations of Cepheid variable stars in another galaxy indicated that the age of the universe is about eight-twelve billion years. Why did her discovery cause such a debate among astronomers? What elements of her discovery still lend themselves to argument?
3. What do scientists learn by observing parts of the universe in other than the visible parts of the spectrum?
4. What materials are believed to compose dark matter, and what can we learn about the universe by examining it?

[edit] Evaluation

Evaluations of the diagrams are as follows:

Three points: diagrams carefully prepared; labels clear and correct; diagrams accurately illustrate the star’s stages of evolution

Two points: diagrams adequately prepared; some labels unclear or incorrect; diagrams accurately illustrate the star’s stages of evolution

One point: diagrams carelessly prepared; labels unclear and/or incorrect; diagrams reflect some inaccurate information about the star’s stages of evolution

Students can contribute to the assessment by determining how many diagrams will be required to illustrate the stages of evolution for each type of star.

[edit] Extra

• Cepheid variables, supernovae, dark matter, cosmic background radiation, black holes, red shift.

[edit] Readings

• w:Astronomy
  • w:Star
    • w:Stellar evolution

etc...