Groups of stars 26.4

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Groups of stars 26.4

  1. 1. Groups of Stars 26.4 Star Systems Star Clusters Galaxies
  2. 2. Star Systems <ul><li>Star System is two or more stars held together by gravity. </li></ul><ul><li>More than half of all stars are part of a star system </li></ul><ul><li>A two star system = binary star </li></ul><ul><li>Eclipsing binary = One star may pass around another </li></ul>
  3. 3. Star Cluster <ul><li>Why study star clusters? </li></ul><ul><li>All stars formed together in the same nebula (space cloud) so can find ages of stars and clusters. </li></ul><ul><li>3 kind of clusters </li></ul><ul><li>Open, Associations, Globular cluster </li></ul>
  4. 4. 3 kind of clusters <ul><li>Open cluster = has a disorganized, loose appearance contains a few thousand stars spread out </li></ul><ul><li>Associations cluster = are temporary groupings of bright young stars – </li></ul><ul><li>Get pulled apart by gravity – </li></ul><ul><li>Larger than open clusters </li></ul>
  5. 5. Globular Clusters <ul><li>A large group of old stars </li></ul><ul><li>Lack dust and gas to form new stars </li></ul><ul><li>Contain more than 1 million stars </li></ul><ul><li>No short lived blue stars—they died </li></ul><ul><li>Oldest 12 billion years old </li></ul><ul><li>Therefore the universe is that OLD </li></ul>
  6. 6. Galaxies <ul><li>Classified into 4 categories: </li></ul><ul><li>Spiral, Barred-spiral, Elliptical, and Irregular </li></ul><ul><li>Spiral & Barred-Spiral = </li></ul><ul><li>Have a bulge of stars at the center </li></ul><ul><li>With arms extending outward like a pinwheel </li></ul><ul><li>If Barred has a bar on either side of arms </li></ul>
  7. 7. Elliptical Galaxies <ul><li>Spherical or Oval </li></ul><ul><li>Has wide range of sizes </li></ul><ul><li>Have little dust and gas between stars </li></ul><ul><li>No new stars forming in older EG </li></ul><ul><li>Contain only old stars </li></ul>
  8. 8. Irregular Galaxies <ul><li>Small fraction of all galaxies </li></ul><ul><li>Have a disorganized appearance </li></ul><ul><li>Have many shapes </li></ul><ul><li>Typically smaller than other types of galaxies </li></ul><ul><li>Often located near large galaxies with strong gravity = gives shape </li></ul>

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