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Galaxies

Galaxies. Milky Way and Beyond. Galaxies. DAY 1: Types of Galaxies. Galaxy. A large system of stars held together by mutual gravitation and isolated from similar systems by vast regions of space http://dictionary.reference.com/browse/galaxy. Classification Activity. Worksheets

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Galaxies

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  1. Galaxies Milky Way and Beyond

  2. Galaxies DAY 1: Types of Galaxies

  3. Galaxy • A large system of stars held together by mutual gravitation and isolated from similar systems by vast regions of space • http://dictionary.reference.com/browse/galaxy

  4. Classification Activity • Worksheets • http://btc.montana.edu/CERES/html/Galaxy/gal1.html

  5. Major Types • Spiral • Barred Spiral • Elliptical • Lenticular • Irregular

  6. Spiral • Central spherical “hub” • Hub consists of old red and yellow stars • Flattened disk of gas and dust • Stars occur throughout the disk • Young blue and white stars are found in the spiral arms • Space between the arms looks empty but is also full of stars • Spherical “halo” region above and below disk • The halo contains globular clusters and stray stars

  7. Spiral Arms • The arms are rotating regions of star formation NOT rotating chains of stars • They consist of a “density wave”- a region that moves more slowly than the galaxy itself • The increased density helps to trigger the collapse of gas clouds and start star formation

  8. SPIRAL EXAMPLE • ANDROMEDA GALAXY (Andromeda)

  9. Barred Spiral • The majority of spiral galaxies have a straight bar on either side of the nucleus

  10. BARRED SPIRAL EXAMPLE • SCULPTOR GALAXY (Sculptor)

  11. Elliptical • Ball shaped • Each star orbits the dense core in its own path not confined to any direction • Almost all stars are yellow and red • Rarely any star-forming gas and dust • Ellipticals are described according to their degree of elongation

  12. ELLIPTICAL EXAMPLE • M87 (Virgo)

  13. Lenticular • Intermediate type of galaxy • Dominated by a roughly spherical nucleus • old red and yellow stars • Disk of stars and gas • No spiral arms • Little sign of star formation

  14. LENTICULAR EXAMPLE • NGC 2787 (Ursa Major)

  15. Irregular • Galaxies that don’t fit other categories • “Peculiars”= • Galaxies colliding with companions or being pulled apart by neighbour’s gravity. • “True Irregulars”= • Contain a lot of gas, dust and hot blue stars. • Great waves of star formation. • Frequently have vast, pink emission nebulae.

  16. IRREGULAR EXAMPLE • CIGAR GALAXY (Ursa Major)

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