Stars & Gallaxies


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8th science, evolution of stars, milky way, and types of galaxies

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Stars & Gallaxies

  1. 1. Stars & Gallaxies CMS Obj. 3-5 Describe the appearance & nature of our galaxy & the universe State Correlation: #7
  2. 2. What you will Learn <ul><li>Measurement in Space </li></ul><ul><li>Evolution of Stars </li></ul><ul><li>Types of Galaxies </li></ul><ul><li>Identify & Describe the Milky Way </li></ul><ul><li>Identify & Describe Objects in the Universe </li></ul>
  3. 3. Star Magnitude <ul><li>Why are some stars Brighter? </li></ul><ul><ul><li>Absolute Magnitude : Measure of the amount of light actually given off </li></ul></ul><ul><ul><li>Apparent Magnitude : Measure of the amount of light received on Earth </li></ul></ul>
  4. 4. How far away are stars? <ul><li>Parallax : apparent shift in the position of an object when view from two different locations </li></ul><ul><ul><ul><li>measures the distance of stars from earth that are relatively close </li></ul></ul></ul><ul><li>Light Years : Unit of measurement for large distances in space </li></ul><ul><ul><ul><li>Distance light travels in 1 year </li></ul></ul></ul><ul><ul><ul><li>Light travels 300,000 km/s or 9.5 trillion km /year </li></ul></ul></ul><ul><li>Proxima Centauri : closest star to earth </li></ul><ul><ul><li>(4.3 light years away – 40 trillion km) </li></ul></ul>
  5. 5. Star C o l o r <ul><li>Indicates temperature </li></ul><ul><ul><li>Hot Stars: Blue /W hite </li></ul></ul><ul><ul><li>Cool Stars – Red / Orange </li></ul></ul><ul><ul><li>Medium Stars – Yellow like our Sun </li></ul></ul>
  6. 6. Hertzsprung-Russell diagram (H-R): <ul><li>shows the relationship between the absolute magnitude of a star and its temperature </li></ul>
  7. 7. Evolution of a Star <ul><li>Nebula : large cloud of gas, plasma & dust within a galaxy where star formation takes place </li></ul><ul><ul><li>A star is born by fusion of hydrogen at 10 million K </li></ul></ul><ul><li>Main Sequence Star : hydrogen fueled star </li></ul><ul><ul><li>Makes up about 90% of stars </li></ul></ul><ul><ul><li>Can be high or low mass </li></ul></ul><ul><ul><li>Our sun is main sequence </li></ul></ul><ul><li>Giants : fueled by helium from a low mass star </li></ul><ul><ul><li>Outer layers Cool & expands with a carbon core </li></ul></ul><ul><li>White dwarf : outer layer of giant escapes into space, core contracts leaving a hot dense small star </li></ul><ul><li>Super Giant : fueled by helium from a high mass star </li></ul><ul><ul><li>Outer layers Cool & expands with an iron core </li></ul></ul><ul><ul><li>Neutron star : collapsed core of super giant with extremely high density </li></ul></ul><ul><ul><li>Super Nova : exploding star </li></ul></ul><ul><ul><ul><li>Black Hole : tremendously big supernova that collapses to a point of no volume </li></ul></ul></ul>
  8. 8. Black Holes Neutron Stars
  9. 10. Galaxies <ul><li>Huge collection of stars, gas, & dust </li></ul>
  10. 11. Three Types of Galaxies <ul><li>Elliptical : range from spherical to elliptical </li></ul><ul><ul><li>No typical size or brightness </li></ul></ul><ul><ul><li>Contains old cool red stars & small amounts of gas & dust, so no new stars are forming </li></ul></ul><ul><ul><li>Most common type </li></ul></ul><ul><li>Spiral : stars arranged in two or more spiral arms </li></ul><ul><ul><li>New blue stars form in arms </li></ul></ul><ul><ul><li>Center is often bulging disk of older red stars </li></ul></ul><ul><ul><li>Barred Spiral : sub-group with a vast straight bar of stars lying across the center with a spiral arm at the end of each bar </li></ul></ul><ul><li>Irregular : lack regular pattern & shape, and are small & faint </li></ul><ul><ul><li>Two types: colliding & gravitational interaction distorting the shape </li></ul></ul><ul><ul><li>Mixture of young & old stars with lots of gas & dust for new star formation </li></ul></ul>
  11. 12. Galaxies
  12. 13. Our Galaxy - The Milky Way <ul><li>Normal Spiral </li></ul><ul><li>About 100,000 light-years in diameter </li></ul><ul><li>Contains between 200 billion & 400 billion stars </li></ul><ul><li>About 14 billion years old </li></ul><ul><li>3 basic parts: </li></ul><ul><ul><li>Bulge </li></ul></ul><ul><ul><li>Disk </li></ul></ul><ul><ul><li>Halo </li></ul></ul>
  13. 14. Milky Way
  14. 15. Central Bulge <ul><li>Mostly older stars </li></ul><ul><li>Small amounts of gas and dust </li></ul><ul><li>Very little star formation </li></ul>
  15. 16. Disk <ul><li>Flattened area containing the spiral arms that are pin-wheeled shaped </li></ul><ul><li>Our solar system is located on the Orion Arm 25,000 light-years away from the central bulge </li></ul><ul><li>Galactic Clusters : vast cloud of dust & gas that forms a group of stars </li></ul><ul><ul><li>Contains a few dozen to thousands of stars </li></ul></ul><ul><ul><li>Interstellar matter is thin but widespread </li></ul></ul><ul><ul><li>Bound together with gravity by a common origin </li></ul></ul><ul><ul><li>Also know as an open cluster because they break apart </li></ul></ul><ul><ul><li>Believed to be what forms the spiral arms </li></ul></ul>
  16. 17. Halo <ul><li>Sphere of gas & stars surrounding the central bulge & disk </li></ul><ul><li>Thought to be 100’s of thousands of light-years across </li></ul><ul><li>Oldest stars in the galaxy </li></ul><ul><li>Stars travel in clumps called… </li></ul><ul><ul><li>Globular Clusters: tight gravitationally bound concentration of approximately 10 thousand to one million stars that do not break apart </li></ul></ul><ul><li>Dark Matter: does not produce or reflect light </li></ul><ul><ul><li>Has a gravitational effect that can be detected </li></ul></ul><ul><ul><li>Believed to be the most common material in the Milky Way </li></ul></ul>
  17. 18. Dark Matter END
  18. 19. Nebula <ul><li>Most are just a few light-years wide </li></ul><ul><li>2 main types </li></ul><ul><ul><li>Planetary Nebula: forms when a star collapses and throws off some of its outer materials to form a cloud </li></ul></ul><ul><ul><li>Diffuse Nebula: also known as a gaseous nebula because it is a huge cloud of gas and dust with regions of new star formation </li></ul></ul><ul><ul><ul><li>There is no star in its center </li></ul></ul></ul>
  19. 20. Light Year Video BACK
  20. 21. Proxima Centauri BACK