Galaxies
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Galaxies

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Galaxies Galaxies Presentation Transcript

  • Galaxies Galaxy Field – Hubble Telescope
  • Hubble Classification of Galaxies (3)      All bright galaxies fall into one of 3 broad classes according to their shape. 75% - Spiral 20 % - Elliptical 5 % - Irregular Basic classification system developed by Edwin Hubble (1936).
  • Hubble “Tuning Fork” Diagram
  • I. Spirals (2) a) Normal Spirals  Classified by its relative strength of the central bulge & tightness of the spiral arms. Types: Sa, Sb, and Sc
  •  Sa: Strong bulge and tight, indistinct arms.
  • Sb  Intermediate type
  •  Sc Small central bulge and loose, well defined arms.
  • Examples  The Milky Way (130,000 light years wide)  Andromeda (our nearest galaxy is 2-3 million light years away).
  • b. Type SB Barred Spirals Features a strong central stellar bar.  Bar rotates as a unit (solid body rotation).  Spiral arms emerge from the ends of the bar.
  • Same subclasses a. b. c. SBa SBb SBc
  • II. Ellipticals Structure and Dynamics:  Spheroid of old stars with little gas or dust.  Supported by random motions of stars with a very slow rotation.
  • E0
  • E1
  • E3
  • III. Irregulars Structure and Dynamics:     Chaotic structure and movement. No definite pattern. Lots of young blue stars. Moderate rotation in Irregulars, but very chaotic motions as well.
  • Our Milky Way     Spiral Galaxy. Our sun is just one of the perhaps 100 billion stars that make up the Milky Way. The sun is located about 28,000 light years from the center of the Milky Way. The Milky Way galaxy is ~100,000 – 130,000 light years in diameter.
  • You are here.
  • 3 parts of the Milky Way 1. Disk – flat rotating frisbee shaped part of the galaxy. 100,000 – 130,000 light years in diameter.
  • 2. Bulge – the dense roughly spherical concentration of stars at the center of disk.  Roughly 24,000 light years from the sun.
  • 3. Halo – is sparsely populated extended region that encompasses the disk and bulge of the galaxy. The brightest members of the halo are large star clusters, known as globular clusters.