December 18, 2013 What do you know about the life of a star?
Bellwork December 18, 2014 What determines the life cycle and life time of a star?
Scale 4 3 2 1 0 I am a 3 and can apply the stages to the HR diagram I can describe all of the stages of a star s life and what factors determine the star s life stages and length of life I can partially describe the stages of a star s life I understand that the stars have a life cycle but I do not understand the order of the stages I don t know anything the life cycle of stars
Essential Question What factors determine the life stages and length of a star s life?
Initial Thoughts Part I - Life Cycle of a Human: Open the bag and take out the pictures of humans. Put them in order from youngest to oldest. Part II Life Cycle of Stars: Take out the pictures of stars. Put them in order from youngest to oldest. Part III Reflection: Reflect in the initial thoughts section about how accurate you think your predictions were.
Why Humans vs Stars??
Human Life Cycle Order
LIFE CYCLE OF STARS Essential Question: What are the factors that affect a star s life cycle? Initial Thoughts: Explain how you did in the initial thoughts activity Flow Map: LIFE CYCLE OF STARS Create a flow map that will compare the life cycle of a medium sized start to a large star. Life Cycle of a Star Foldable What Affects a Star s Life Cycle? How does the HR Diagram show a star s life cycle? Conclusion: Page # Page #
Life Cycles of Humans vs. Stars
Formation of a Protostar All stars begin from a nebula and form a protostar. **When did we learn about this already?** A portion of the nebula (dust and gases) begins to shrink due to its gravity. As the pressure and temperature increase, the new star begins nuclear fusion. As the new star equalizes in pressure and gravity, it becomes a star (its next stage of life). Vocabulary: Nebula-A diffuse mass of interstellar dust and gas. Protostar-Very dense regions (or cores) of molecular clouds where stars are in the process of forming.
Nebula
Protostar
Star s Life (Main Sequence) For a star to live, it must produce energy through fuel (made up of elements like Hydrogen and Helium). A star s energy is produced through nuclear fusion. Once all the Hydrogen is used, the star proceeds to its next stage. Stars spend about 90% of their life at this stage.
Main Sequence Star (our Sun)
Middle Age of a Star When the star is completing its hydrogen fuel, the star begins to collapse and then begins to swell. The star will then begin burning helium producing larger elements. The star will become much brighter than at the previous stage. Vocabulary: Red Giant - A star that has run out of hydrogen and is burning heavier elements. This star expands as it burns.
Our Sun Compared to other Stars
A Star s Old Age to Death Medium Stars Cool at the end of the Red Giant stage faster than larger stars, so they begin to shed its gases outside its core forming a planetary nebula. The center of the small star then begins to cool to become a white dwarf and cools more to become a black dwarf. Large Stars Larger stars are hotter than small stars but still need more energy for the core of the star to collapse. During a supernova, the star completely collapses. Depending on the original size of the star, either a neutron star or black hole will be created.
Sun as a red giant
The Sun as a white dwarf
A Star s Old Age to Death Vocabulary: Planetary Nebula-a shell of gas discarded by a medium star white dwarf-a star that has exhausted most or all of its nuclear fuel and has collapsed to a very small size black dwarf-a non-radiating ball of gas resulting from a white dwarf that has radiated all its energy. supernova -The death and explosion of a massive star, resulting in a sharp increase in brightness followed by a gradual fading black hole-an object whose gravity is so strong that not even light can escape from it. Neutron Star-a small and highly dense star consisting of neutrons and is the remains of a massive star
Supernova Explosion
Medium Stars vs. Large Stars Review your foldable and look for any items that refer any size of star highlight or underline this with green Review your foldable and look for any items that refer to medium sized stars highlight this with blue Review your foldable and look for any items that refer to large sized stars highlight this with red
Try to organize the star pictures Now that we have discussed the different stages of a stars life, try to organize the pictures of the stars again.
What factors affect stars? What factor causes the star s life cycle to be one path instead of another? MASS of the star Look at the life cycle map. What size stars become blackholes? What size become black dwarfs? Massive stars become black holes. Average and small stars become black dwarfs. What factor causes the star to live longer than another star? MASS of the star http://aspire.cosmic-ray.org/labs/star_life/begin_stars_real.html Do small stars live longer or shorter? SMALL stars live longer because they go through fusion slower than large stars.
HR Diagram and Life Cycle HR Diagram is an illustration of star size, brightness, and star color. How does the location of a star on the HR diagram change as its lives the stages of its life cycle? http://sunshine.chpc.utah.edu/labs/starlife/support/h R_animated_real.html
Conclusion 1. What are the stages of a star s life cycle? 2. What determines which stages a star will live? 3. What size star allows it to live a long life? 4. What stage does all stars live? 5. When a giant star dies, what would it then be?
Scale 4 3 2 1 0 I am a 3 and can apply the stages to the HR diagram I can describe all of the stages of a star s life and what factors determine the star s life stages and length of life I can partially describe the stages of a star s life I understand that the stars have a life cycle but I do not understand the order of the stages I don t know anything the life cycle of stars
January 5, 2012 How does mass affect a star s life? DON T FORGET TO FINISH YOUR STUDY GUIDES!!!