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Cosmology and QSO’s. Edwin Hubble. Red Shift and Distance. 24 Mpc. 1200 km/s. 300 Mpc. 15,000 km/s. 780 Mpc. 39,000 km/s. 1220 Mpc. 61,000 km/s. Hubble’s Result. Modern Hubble’s Law. 2. 2. 1. 1. 3. 3. Raisin Cake Model. Velocity. Distance. Raisin Cake Model. Velocity

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red shift and distance
Red Shift and Distance

24 Mpc

1200 km/s

300 Mpc

15,000 km/s

780 Mpc

39,000 km/s

1220 Mpc

61,000 km/s

raisin cake model7

Velocity

Distance

Raisin Cake Model

Velocity

1 cm/hr

2 cm/hr

3 cm/hr

Distance Distance

from Home from Home

(before baking) (after baking)

1 1 cm 2 cm

2 2 cm 4 cm

3 3 cm 6 cm

hubble s law to get distance
Hubble’s Law to get Distance
  • Measure the red shift of a galaxy
    • Compute the radial velocity
  • Use Hubble’s Law to get the distance
    • Assumes that red shift is caused by radial velocity and that radial velocity is caused by the universal expansion.
universal expansion
Universal Expansion
  • Space-Time itself is expanding
    • Carries galaxies along with it
  • Conflicting cosmologies
    • Big Bang
      • Draw the expansion back in time until space-time occupies a point (13.7 billion years ago)
    • Steady State
      • Requires continual creation of matter
quasi stellar objects
Quasi-Stellar Objects
  • Extreme red shift
    • Using Hubble’s Law gives great distance
    • Visibility at these distances requires huge luminosity
  • Almost star-like
  • Variable
    • Using Light Time Argument gives size of solar system
qso 3c 273 and its jet
QSO 3C 273 and its jet
  • Red Shift of 16%
  • Distance 800 Mpc
  • Luminosity of 1000 normal galaxies
the record red shift
The RecordRed Shift

La normally at 1216 Å

cosmological hypothesis
Cosmological Hypothesis
  • QSO’s are at the distance implied by Hubble’s Law
    • Most distant objects in the universe
    • Extreme luminosities
  • But their light variations limits the size to roughly solar system
    • Emit as much light as 1000 large galaxies in the space of a solar system

What is the energy source?

local hypothesis
Local Hypothesis
  • QSO’s are nearby
    • Distances of normal galaxies
    • Luminosities don’t have to be as great

What causes the Red Shift?

the red shift dilemma
The Red Shift Dilemma
  • Mass ejection
    • Perhaps QSO’s are matter violently ejected from galactic nuclei. Recall M87
    • Why only Red Shifts?
  • Gravitational Red Shifts
    • Light loses energy in escaping a gravity field
      • E = hf = hc/l
      • If energy decreases, wavelength increases
    • Impossible to get the large red shifts required
additional facts
Additional facts
  • If QSO’s are very distant, we are seeing them as they were long ago.
  • Gravitational lens
quasar gravitational lenses

Q 0142

Q 0957+561

H 1413+117

Quasar Gravitational Lenses
summary

QSO’s

Velocity

BL Lac Objects

Seyfert Galaxies

Normal Galaxies

Distance

Summary
  • QSO are active galactic nuclei
    • Early stage of galaxy formation
model of a quasar
Model of a Quasar
  • Supermassive Black Hole forms in the center of a galaxy
    • 108 - 109 M
    • Event Horizon size of solar system
  • Thick accretion disk fuels the activity
    • as disk thins quasar dims
normal galaxies harbor supermassive black holes
Normal Galaxies Harbor Supermassive Black Holes
  • Measure luminosity of the nucleus
    • Mass in the form of stars
    • Brightness predicts mass
  • Measure speed of the stars near the nucleus
    • Stars move under the influence of gravity
    • Gravity caused by mass at the nucleus
  • Many galaxies have large, underluminous mass at the center