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