Astronomy - Chapter 4 - Galaxies and Cosmology - Galaxies

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  • Created on: 10-04-13 17:06
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  • Astronomy - Chapter 4 - Galaxies and Cosmology - Galaxies
    • Galaxies
      • Elliptical
        • These appear as a white fuzzy circle or ellipse
        • Depending on how stretched the ellipse is these galaxies are given the numbers E0 (circular) to E7 (highly elliptical/elongated)
        • relatively smooth spheroidal
      • Spiral
        • These galaxies show a central bulge, or nucleus, off which spiral arms of the galaxy; these galaxies are classi?ed from Sa to Sc
        • They are flattened - when seen edge-on they are long and thin
        • Flattened disk-shaped systems e.g Andromeda Galaxy and M81
        • Milky Way = Sb galaxy
      • Barred Spiral
        • Similar to spiral galaxies but have a 'bar' running through the nucleus
        • These galaxies have a nucleus with a bar shape extending either side of the central bulge
        • These Galaxies are shown/classified from SBa to SBc
      • Irregular
        • They have very little structure or symmetry
        • These come in all shapes and sizes
    • Local Group
      • Our Galaxy is a member of the Local Group
      • The Local Group consists of 50 galaxies
      • Some galaxies are:
        • Andromeda - largest in the group
        • Large and Small Magellanic Clouds
        • Triangulum Galaxy
        • Dwarf Galaxies - Pisces Dwarf and Aquarius Dwarf
      • The group is 3MPC across
    • Active Galaxies
      • Radio galaxies
        • Discovered in the 1950's and mainly elliptical
        • They emit more than million times more energy at radio wavelengths than normal galaxies
      • Seyfert galaxies
        • Discovered by Carl Seyfert in 1943 and are extremely compact but have a bright nuclei
        • Strong emission lines in their spectra show strong and often IR and X-ray radiation
        • Spiral Galaxy
      • Quasars
        • Discovered by radio astronomers in 1963
        • They a compact appearance which makes them look like stars
        • They emit huge quantities of energy in all regions of the spectrum from X-rays and radio waves
        • They also emit huge amounts of redshift which makes them the most distance objects in the universe
      • Blazars
        • Discovered in the 1970's
        • They also appear star-like but lie much closer than quasars
        • They emit stronger radiation from gamma-rays to radio waves
      • Active Galactic Nuclei are powered by matter falling into the super massive BLACK HOLE at the centre
    • Clusters and Super Clusters
      • Our closest cluster is the Virgo Cluster
      • Clusters are galaxies which have grouped together
      • Superclusters are clusters that have grouped together


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