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Chapter 30 Stars and Galaxies Slide 2 SOAR Chapter 30 Standard 1d. Students know the evidence indicating that the planets are much closer to the Earth than the stars. 2d. Students know that the stars differ in their life cycles and that visual, radio, and Xray telescopes may be used observe them. 1e.Students know that our sun is a typical star and is powered by nuclear reactions. Objective 1Describe our sun and explain how it works. Objective 2Describe the composition of stars. Objective 3Describe how astronomers measure distances to stars. Objective 4Describe star formation and evolution. Objective 5Identify the 3 types of galaxies. Assessment and ReviewDaily bellwork, science starters, Chapter 30 Test Slide 3 Key Terms Create a flashcard for each of the following (they begin on page775): Star Light-year Parallax Main sequence Giant White dwarf Nova Neutron star Pulsar Black hole Slide 4 Our Sun A typical, average star 75% of the sun is Hydrogen, the rest is Helium Nuclear Fusion= 2 Hydrogen atoms fusing to become one Helium atom. Nuclear Fusion creates a tremendous amount of energy Slide 5 Our Sun Brainpop Slide 6 Stars All stars are balls of gases that give off extreme amounts of energy due to Nuclear Fusion Stars are made of mostly Hydrogen and Helium with some Carbon, Oxygen, Nitrogen The temperature of a star is indicated by its color. Slide 7 Distances to Stars Distances between stars are measured in light years For closer stars Scientists use PARALLAX to determine its distance from Earth. PARALLAX=the apparent shift of a stars position when viewed from different positions. One star might appear in the left of the sky in January but on the right of the sky in June Slide 8 Slide 9 Parallax Clip Slide 10 Classifying Stars Scientists use radio, X-ray, and Visual telescopes to classify stars H-R Diagram is used to organize the stars by Luminosity and Temperature Slide 11 Star Life Cycle Brain Pop Slide 12 Life Cycle of a Star Nebula All stars begin as a cloud of dust and gas Protostar Gravity pulls the nebula together and when temps increase to 10 million degrees, nuclear fusion begins and a star is born Main- Sequence Longest stage of a stars life Energy continues to generate by way of nuclear fusion Slide 13 Giant Stars As he hydrogen atoms deplete the star contracts Then the core becomes hotter, causing the star to expand larger than before As they cool they glow redRED GIANT Super Giants If the star was massive, they become SUPERGIANTS Final Stages Planetary Nebula: The gases drift away leaving a nebula White Dwarf: After the gases of the planetary nebula drift away the remaining matter collapses and gravity pulls it together creating a WHITE DWARF..they shine for billions of years until cool Black Dwarf: When the white dwarf is completely cool and no longer gives of lightmany scientists do no believe these exist yet Slide 14 Novas In a binary system, if a white dwarf revolves around a red giant an explosion can occur= NOVA Supernova Massive stars become Red Supergiantsthe gravity is so great hat fusion of heavier elements (Carbon) begins until all the fuel is gone With the fuel gone the core collapses and the star explodes Neutron Stars After a supernova the leftover core may become a very dense ball of neutrons Neutron Stars rotate very rapidly Slide 15 Pulsars Neutron stars that emit a beam of radio waves Like a lighthouse Black Holes Remaining core after a supernova contracts under its own gravity but is SO MASSIVE that is leaves a black hole Gravity is so great that not even light can escape it Black Holes cannot be seen but their effect on their companion stars can be seen (the second star orbits around seemingly nothing) Slide 16 Life Cycle of a Star Slide 17 INTERACTIVE Comic Strip/Cartoon of our stars (the sun) life cycle Picture and text for each segment (use p.786- 787 to help) Nebula Protostar Main-Sequence Red Giant Planetary Nebula White Dwarf Slide 18 Types of Galaxies Galaxies account for most of the visible mass in the universe. Spiral Elliptical Irregular Slide 19 Assessment/Interactive Complete the Maps in Action Activity on page 804. Left Hand side of your notebook Do NOT copy the question, but answer in complete sentences Read the Science and Tech. article on page 805 Answer question 1 Write a half-page summary