My lecture on the history of cosmology, how our understanding of the universe we live in improved in the 20th century and the great debate.

1. ISLAND UNIVERSES

2. The Great Debate
What if one walk to the end of the world?

3. 905: Sufi (small cloud)

4. 18th Charles Messier: Catalogs of nebulous objects

5. 1758: Hershel: Andromeda is
the nearest great nebulae.

6. 1845 Lord Ross: Elliptical, spiral nebulae

7. 1864: William Huggins
Spectrum of Andromeda is
similar to stars (continuous
and superimposed by dark
lines)

8. 1885 Supernova
S-Andromeda
Type Ia

9. Type I Supernovae
 Binary system
 One is greater in mass
 AGB: Rapid mass loss -> angular momentum
 …White dwarf attracts the mass of the
companion
 Mass loss -> Orbit period: hours!

11. Nova
 Roche Lobe
 Astronaut orbiting space shuttle
 Hill Sphere
 The largest sphere, centered at the second
body, within which the sum of the three fields is
always directed towards the second body. A
small third body can orbit the second within the
Hill sphere.

12. Nova
 Accretion
 Fusion of H and He
 Nova is a variable star
 RS-Oph

14. Type I Supernovae…
 WD reaches Chandrasekhar limit
 The limit is never attained
 Increase of pressure -> T near core
 Convection for 1000 years
 Carbon fusion (unknown)
 Oxygen fusion

15.  Fusion -> Raises T
 A MS star expands but WD has degeneracy
pressure
 The story of cold plasma, Pauli, Heisenberg
 P = Kn5 / 3 instead of PV = NkT
 T has minor effect on pressure -> Nothing to
stop T raising
 Instability

16. Instability

17.  Thermonuclear explosion
 1046 j -> Unbind the star
 Abs. Mag. = -19.3!
 Type I supernovae are found all around the
world, elliptical glx, GCs, etc. And S-And.
 Standard Castle

18. SN Type Ia. It takes months for SN to dim

20. The Great Debate April 26 1920
On The Scale of The Universe
Harlow Shapley Heber Curtis

21. The Great Debate
 Harlow Shapley  Heber Curtis
 Milky Way is the entire  Andromeda has more
universe novae than observed in
 Andromeda’s observed the entire sky
rotating (speed of  SN S-And
light)  Island Universes

22. Andromeda (M31) Galaxy

23. Milky Way

26. Celestial Coordinate Systems

27. Equatorial Coordinates

30. Shapley’s GCs Method

31. Galactic Coordinates