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Announcements. 4th test is finished! Please pick up graded work Homework 12 due Monday (requires internet use) Second project is due in two weeks Please reread lyrics to Monty Python galaxy song; document the inconsistency for a free Milky Way bar!. Galaxies. 17 November 2006. Today :.

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Announcements
Announcements

  • 4th test is finished!

  • Please pick up graded work

  • Homework 12 due Monday (requires internet use)

  • Second project is due in two weeks

  • Please reread lyrics to Monty Python galaxy song; document the inconsistency for a free Milky Way bar!


Galaxies

Galaxies

17 November 2006


Today
Today:

  • The “spiral nebulae”

  • Measuring distances to galaxies

  • Rotation rates and “dark matter”


Messier catalog
Messier Catalog

  • 27 “open” clusters

  • 29 globular clusters

  • 6 diffuse nebulae

  • 4 planetary nebulae

  • 1 supernova remnant

  • 2 small groups of stars

  • 40 other fuzzy things in which no individual stars are visible



What are the spiral and elliptical nebulae
What are the spiral and elliptical nebulae?

  • No individual stars are visible, even in largest telescopes

  • Some have spiral structure, as if spinning rapidly

  • Visible amount of rotation over a few decades?

  • Continuous spectra

  • Hypothesis 1: Swirling clouds of fluid, possibly forming new solar systems

  • Hypothesis 2: “Island universes,” similar to our own Milky Way star system


Island universes confirmed
Island Universes Confirmed!

Edwin Hubble discovers Cepheid variable stars in the Andromeda Nebula, 1923

Estimated distance: 1 million light-years (actually 2 million)

Edwin Hubble, 1889 - 1953











Virgo cluster
Virgo Cluster light-years (Virgo Cluster)


Ngc 253
NGC 253 light-years (Virgo Cluster)


Whirlpool galaxy m51
Whirlpool Galaxy (M51) light-years (Virgo Cluster)


M83 light-years (Virgo Cluster)


M104 sombrero galaxy
M104 (Sombrero Galaxy) light-years (Virgo Cluster)


Edge on galaxies
Edge-on galaxies light-years (Virgo Cluster)


Barred spiral galaxies
Barred spiral galaxies light-years (Virgo Cluster)


Colliding galaxies
Colliding Galaxies light-years (Virgo Cluster)


Galaxy with dust lane
Galaxy with dust lane light-years (Virgo Cluster)


Group of galaxies in leo
Group of galaxies in Leo light-years (Virgo Cluster)



Coma cluster
Coma Cluster type-I supernovas


Coma cluster1
Coma Cluster type-I supernovas


Hubble deep field
Hubble Deep Field type-I supernovas


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