announcements 4th test is finished! please pick up graded work homework 12 due monday (requires...
TRANSCRIPT
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!
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?
• 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!
Edwin Hubble discovers Cepheid variable stars in the Andromeda Nebula, 1923
Estimated distance: 1 million light-years (actually 2 million)
Edwin Hubble, 1889 - 1953