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Notes from Mr. Olandese's DES Class on the different types of Galaxies and how they move.

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  1. 1. Types of Galaxies
  2. 2. Galaxies: <ul><li>A large group of stars, gas, and dust held together by gravity </li></ul><ul><li>May contain as many as one trillion stars that can be millions of light years apart </li></ul><ul><li>Separated by millions of light years from each other </li></ul><ul><li>Grouped into clusters (Our cluster is called the Local Group and contains 30+ galaxies) </li></ul>
  3. 3. 3 Types of Galaxies <ul><li>Spiral Galaxies </li></ul><ul><li>Elliptical Galaxies </li></ul><ul><li>Irregular Galaxies </li></ul>
  4. 4. Spiral Galaxies <ul><li>Have spiral arms that wind outward from inner regions </li></ul><ul><li>Arms are made up of bright stars and dust </li></ul>
  5. 5. Example of Spiral Galaxy <ul><li>Our Galaxy, the Milky Way </li></ul><ul><li>The visible Milky Way suggests our galaxy is a flat disk </li></ul><ul><li>All the stars we can see from Earth are in the Milky Way </li></ul>
  6. 6. The Milky Way As We See It
  7. 7. Example of a Spiral Galaxy <ul><li>The Andromeda Galaxy </li></ul><ul><li>The Andromeda Galaxy (2 million light years away, member of the Local Group) </li></ul>
  8. 8. Elliptical Galaxies <ul><li>Shaped like large 3D ellipses </li></ul><ul><li>Can be football shaped or round </li></ul>
  9. 9. Irregular Galaxies <ul><li>Don’t fit into the other classifications </li></ul><ul><li>Smaller than the other 2 types of galaxies </li></ul><ul><li>Orbit the Milky Way </li></ul>
  10. 10. Who do we know which way galaxies are moving? <ul><li>Doppler Effect </li></ul><ul><ul><li>The wavelength of sound or light emitted by an object is shifted if the object is moving </li></ul></ul><ul><li>If the object is coming toward you, the light is shifted toward shorter wavelengths, blue shifted . </li></ul><ul><li>If the object is going away from you, the light is shifted toward longer wavelengths, red shifted . </li></ul>
  11. 11. Star Light Spectrums <ul><li>Spectrum lines are shifted towards the blue end </li></ul><ul><li>Is this star moving toward you or away from you? </li></ul>
  12. 12. Star Light Spectrums <ul><li>Spectrum lines are shifted towards the red end. </li></ul><ul><li>Is this star moving toward you or away from you? </li></ul>
  13. 13. Doppler Shift <ul><li>The amount of shift is bigger if the emitting object is moving faster. </li></ul><ul><li>Thus if we know the original wavelength, we can figure out the speed. </li></ul><ul><li>We do know the wavelengths of certain elements like Hydrogen (H) and Helium (He). </li></ul><ul><li>Thus for many objects in outer space we can tell </li></ul><ul><ul><li>Is it coming toward us? </li></ul></ul><ul><ul><li>Is it going away? </li></ul></ul><ul><ul><li>If so, how fast is it moving toward us or away from us? </li></ul></ul><ul><ul><li>But this does not tell us how fast it is moving sideways. </li></ul></ul>
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