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The Expanding Universe
Steven BeckwithSpace Telescope Science Institute
US Ambassador’s Residence, New ZealandJuly 8, 2002
Edwin Hubble & Galaxies
5
Doppler Shifts and Galaxy Velocities
z = change in wavelength
wavelength
speed z x speed of light
Measure the redshift, z.Infer the speed, v
Doppler shift of light
speed
6
D = 4D0
v = 4v0
D = 2
D 0
v = 2
v 0
D = 2.5D
0
v = 2.5v0
D = 2.3D 0
v = 2.3v 0
D = 0.9D0
v = 0.9v0
v =
1.4
v 0D
= 1
.4D
0
D =
3.1D0
v = 3.1v
0
Hubble 1929
Velocity = H0 x Distance
7
Modern Hubble diagramRiess, Press, & Kirshner (1996)
Velocity = H0 x Distance
H0 = 70 km/s/Mpc = 23 km/s/106-light-yr
SN 1994dBrightness 1
Distance x Distance
Hubble can see supernova to when the universe was only 30% of its present age, about 4 billion years
Distance 2
Distance 1
18
Supernovae as standard candles
SN97cj
The CfA SN team: Schmidt, Riess, Kirshner, Garnavitch et al.
z = 0.50
SN97cj
19
Hubble diagram showing acceleration
Recession velocity / light speed
14
16
18
20
22
24
26
0.02 0.05 0.1 0.2 0.5 1.0
Fai
ntne
ss
Perlmutter et al. (1998)
Calan/Tololo(Hamuy et al,A.J. 1996)
SupernovaCosmologyProject
fainter
farther away
decelerating
accelerating
Recession velocity is proportional to distance
21
Distant Supernovae & ACS
SN 2002dd at v/c = 1.06Discovery May 11, 2002
The ACS GTO Team: P.I. Holland Ford, Deputy Garth Illingworth, Zlatan Tsvetanov, John Blakeslee and Adam Riess
1996 2002
22
SN 2002dd infrared light curve
Days relative to maximum
1.2
5
m m
agn
itude
: J
Adam Riess, Stefano Casertano & collaborators using NICMOS
24
Composition of the Universe
25
NGC 3132: Planetary nebulaSOME say the world will end in fire, Some say in ice. From what I’ve tasted of desire I hold with those who favor fire. But if it had to perish twice, I think I know enough of hate To know that for destruction ice Is also great And would suffice.
Robert Frost Harper’s Magazine December 1920