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Astonomy 62 Lecture #37Last TimeActive Galactic NucleiGalaxy Evolution

Astonomy 62 Lecture #37Topics for TodayNewtonian CosmologyCritical DensityΛ CosmologyReading for today: 29.1Reading for next lecture: 29.2, 29.3 (pp. 1190-1191)

Astonomy 62 Lecture #37Cosmological PrincipleThe Universe is homogeneousand isotropicHomogeneous = appearing the same at alllocationsIsotropic = appearing the same in all directions

Astonomy 62 Lecture #37t 0≡ NOWr(t) = radius of theexpanding sphericalshellv(t) = expansion velocity ofthe shell(t) = density of mattercontained inside theshellExpandingShellmrv

Density Energy Dynamics GeometryE = 0(Criticallybound)Expandsforeverwithv 0E < 0(Bound)Eventuallyre-collapsesE > 0(Unbound)Expandsforeverwithv 0

Astonomy 62 Lecture #37t 0≡ NOW ct= 3 H t28 G =CriticaldensityExpandingShellr t= t c t =Densityparameterv=Hr

Density Energy Dynamics Geometry=1E = 0(Criticallybound)Expandsforeverwithv 0Flat (k=0)Closed (k>0)1E < 0(Bound)Eventuallyre-collapses1E > 0(Unbound)Expandsforeverwithv 0Open (k

Astonomy 62 Lecture #37t ≡ NOW0Rt= r tr t 0Rt =R =10 0R(t)Scale Factor R(t)is the same forany shell!ExpandingShellRH t= v t=dRt 1v=Hrr td tRt

Astonomy 62 Lecture #37Closed1Flat=1Open1

=0 empty

Data from Type Ia High–Redshift Supernova ProjectMatter density: M= M cDark energy density: = c

Astonomy 62 Lecture #37Closed1Flat=1=0Open1Accelerating≠0

=0 empty

Current Constraintson CosmologicalParametersMatter Density:M = 0.279±0.014Dark Energy Density:= 0.721±0.015Total Density:tot = Ω M + Ω = 1.00±0.03Age of the Universe:t = (13.73±0.12)x10 9 yrt > t H