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Bell Work: 1. What do all stars begin their life as ? Physical Science 5/1 Agenda: Lives of Stars HertzSprung Russell WS Outer Space WS Learning Target: 2. What kind of star will this form? I can descrbe the life cycle of a star. I can explain how stars differ in size, temperature , and color. Homework/Important Dates: What does “proto” mean? ○ 15.3 + 15.4 Book Notes, Vocab. And Outer Space WS due Thursday 5/4 ○ Unit 6 Test on Tuesday 5/16 Physical Science Notes Lives of Stars The Life of Stars Stars start their lives as parts of nebulas. Nebulas are large clouds of gas and dust spread out over a massive area. In the densest part of nebula, gravity pulls the gas and dust so closely together that nuclear fusion starts. The next stage is a protostar, which is the earliest stage of the star’s life. The Life of Stars The mass of the star determine its lifespan. The smaller the star, the longer the life. The size of the star also determines what path it will take as it goes through its cycle. High mass protostars take a different path than lower mass protostars. The Life of Stars The next stage in the life of a star is the main sequence. This is the stage our sun is in. Higher mass stars tend to burn hotter. Low mass stars expand into red giants, while high mass stars expand into supergiants. These are low temperature stars that burn slowly because they have used all their hydrogen. The Life of Stars If it is a low mass star, the next stage after the red giant is the planetary nebula. A The star expands and the parts drift apart, forming a nebula. high mass star will go supernova, suddenly exploding and releasing massive amounts of energy. The Life of Stars Low mass stars leave their cores behind when they turn into planetary nebulas. The core cools and compresses and turns into a white dwarf. White dwarfs have about the same mass as the sun, but they have the size of Earth. Nuclear fusion no longer takes place, but the star continues to shine with leftover energy. The Life of Stars High mass stars have two paths. Neutron stars are the left over cores of the supergiant. They are much like white dwarfs, but a million times denser. Spinning neutron stars are called pulsars. Pulsars emit radiation in predictable patterns. The Life of Stars The other path is a black hole. Only the densest stars become black holes. Nothing can escape the gravity of a black hole, not even light. Scientists can only detect black holes based on how they affect other stellar bodies. Hertzsprung-Russell Diagrams The HertzsprungRussell diagram (HR diagram) is a Bright way for scientists to classify stars and understand how they change over time. The x-axis represents temperature. Dim The y-axis represents absolute brightness. Hot Cold Hertzsprung-Russell Diagrams More than 90% of stars are in the main sequence. Stars in the main sequence have their brightness increase in proportion to their temperature. Stars that have started to die tend to stray off the main sequence. These stars have used up all the hydrogen and started to expand, or are white dwarfs that have already passed through that phase. Hertzsprung-Russell Diagrams Why are the giants so bright, even though they are not so hot? The brightness of a star is based on both its temperature and how big it is Giants are much bigger than main sequence stars, so they have a much larger surface area to emit light. Bell Work: 1. Describe all the stages of a high-mass star’s life. Physical Science 5/2 Agenda: Bill Nye - Space Exploration Spectroscopes Life Cycle of a Star / Absorption Spectrum WS HR Diagram Learning Target: I can describe the life cycle of a star. I can explain how stars differ in size, temperature , and color. Homework/Important Dates: ○ 15.3 + 15.4 Book Notes, Vocab. And Outer Space WS due Thursday 5/4 ○ Unit 6 Test on Tuesday 5/16 ○ H-R Diagram WS due = Friday ○ Life Cycle of a Star WS = Friday Using a Spectrograph Point the slit end of the spectrograph towards the light source. Look through the other end for the spectra that will appear to side of the slit. Compare and contrast the different light sources. Light source Description of Spectra Example observations to look for: Do the colors blend/fade from one to the next or are they separate bands? Which color is dominant? Are any colors missing/separated? Complete Absorption Spectrum WS on the back of Life cycle of a star. Bell Work: 1. Describe all the stages of a lowmass star’s life. Physical Science 5/3 Agenda: Cosmos: A Spacetime Odyssey Learning Target: Homework/Important Dates: ○ 15.3 + 15.4 Book Notes, Vocab. And Outer Space WS due Thursday 5/4 ○ Unit 6 Test on Tuesday 5/16 ○ H-R Diagram WS due = Friday ○ Life Cycle of a Star WS = Friday Bell Work: ○What is a planetary nebula? Physical Science 5/4 Agenda: Review Quiz Review Outer Space WS Learning Target: ○What is a white dwarf? I can descrbe the life cycle of a star. I can explain how stars differ in size, temperature , and color. ○What are neutron stars? Homework/Important Dates: ○What are black holes? ○ Unit 6 Test on Tuesday 5/16 Bell Work: ○Diagram the life of either a low or high mass star. Physical Science 5/15 Agenda: Quiz Unit Test Study Guide Friday Weekly Assignments: 1. Bell Work 2. Notes 3. Book Notes 4. Hertzsprung Russell 5. Outer Space WS 6. Life Cycle of a star WS Homework/Important Dates: Unit 6 Test on Tuesday 5/16