What contribution(s) have been made towards understanding nature/the structure of the Milky Way ?

Galileo-
   •stars make up the Milky Way
   • 'Why are there invisible objects in the night sky?'

William Herschel-
   • Milky Way is disk-shaped!

Harlow Shapely-
   • spiral nebulae are nearby clouds of gas within the Milky Way and did not believe they were beyond the Milky Way
   •believed it was 300,000 light years in diameter (close, it's actually 100,000)

Edwin Hubble-
   • showed that universe was more than just Milky Way
   • Milky Way is one of many galaxies
   •zone of avoidance around Milky Way

RR Lyrids and Cepheids-
   • good 'candles' for things within Milky Way
   • about 85,000 in Milky Way

Immanuel Kant-
   • many stars are outside of Milky Way

Henrietta Leavitt-
   • 'Period-Lumionosity Relationship' to measure distances in the universe
   • increased assistance in Hertzsprung with distances of Cepheids in Milky Way

Herber Curtis-
   • role in Great Debate with Harlow Shapely
   • spiral nebulae a are actually spiral galaxies outside of Milky Way

"The Great Debate"
   • Shapely v. Curtis
   • 1920
   • nature of spiral nebula and size of universe
   • Shapely= spiral nebulae are inside Milky Way - increased size of universe
   • Curtis= spiral nebulae are galaxies outside Milky Way