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
- Elliptical
- 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
- MOST POWERFUL GALAXIES IN THE UNIVERSE
- 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
- Radio galaxies
- 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
- Galaxies
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