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GALAXIES

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  1. GALAXIES

  2. What is a galaxy? • Galaxies are huge collections of stars, gas and dust held together by gravity.

  3. Galaxy Background Info • The first galaxies were identified as far back as the 17th Century by a French Astronomer called Charles Messier. • Messier compiled a list of 110 star clusters which he discovered while searching the sky for comets.

  4. Edwin Hubble • In the 1920's Edwin Hubble measured the distance to one of these star clusters. • Proved it was located outside our galaxy. • First to classify galaxies.

  5. Today we use Hubble’s Tuning Fork Diagram to classify galaxies.

  6. Types of Galaxies • Elliptical • Spiral • Barred Spiral • Irregular

  7. ELLIPTICAL • Very little dust and gas • Contains primarily old, red stars • Vary is size

  8. Elliptical

  9. SPIRAL • 2 Distinct Regions • Disk • Contains spiral arms • Region of star formation • Large amount of gas and dust • Bulge • Devoid of gas and dust • composed primarily of Population II stars

  10. Barred Spiral

  11. IRREGULAR • do not fit into either the spiral or elliptical classes • wide variety of shapes and characteristics • The result of collisions between galaxies or gravitational interactions between galaxies.

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