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

Raisin Cake Model

12

3

1

2

3

Raisin Cake Model Distance Distance from Home from Home(before baking) (after baking)

1 1 cm 2 cm2 2 cm 4 cm3 3 cm 6 cm

Velocity

1 cm/hr2 cm/hr3 cm/hr

Vel

ocit

y

Distance

Hubble’s Law to get Distance

Measure the red shift of a galaxyCompute 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

Space-Time itself is expandingCarries galaxies along with it

Conflicting cosmologiesBig Bang

Draw the expansion back in time until space-time occupies a point (13.7 billion years ago)

Steady StateRequires continual creation of matter

Arno Penzias & Robert Wilson

Quasi-Stellar Objects

Extreme red shiftUsing Hubble’s Law gives great distanceVisibility at these distances requires huge

luminosity

Almost star-likeVariable

Using Light Time Argument gives size of solar system

QSO 3C 273 and its jet

Red Shift of 16%Distance 800 MpcLuminosity of 1000

normal galaxies

The Spectrum of 3C 273

L normally at 1216 Å

The RecordRed Shift

Cosmological HypothesisQSO’s are at the distance implied by

Hubble’s LawMost distant objects in the universeExtreme luminosities

But their light variations limits the size to roughly solar systemEmit as much light as 1000 large galaxies in the

space of a solar system

What is the energy source?

Local Hypothesis

QSO’s are nearbyDistances of normal galaxiesLuminosities don’t have to be as great

What causes the Red Shift?

The Red Shift Dilemma

Mass ejectionPerhaps QSO’s are matter violently ejected

from galactic nuclei. Recall M87Why only Red Shifts?

Gravitational Red ShiftsLight loses energy in escaping a gravity field

E = hf = hc/If energy decreases, wavelength increases

Impossible to get the large red shifts required

Additional facts

If QSO’s are very distant, we are seeing them as they were long ago.

Gravitational lens

Quasar Gravitational Lenses

Q 0957+561 Q 0142

H 1413+117

Gravitational Lensing

Einstein Ring

Active Galactic Nuclei

Summary

QSO are active galactic nucleiEarly stage of galaxy formation

Vel

ocit

y

Distance

QSO’s

BL Lac Objects

Seyfert Galaxies

Normal Galaxies

Model of a Quasar

Supermassive Black Hole forms in the center of a galaxy108 - 109 M

Event Horizon size of solar system

Thick accretion disk fuels the activityas disk thins quasar dims

Normal Galaxies Harbor Supermassive Black Holes

Measure luminosity of the nucleusMass in the form of starsBrightness predicts mass

Measure speed of the stars near the nucleusStars move under the influence of gravityGravity caused by mass at the nucleus

Many galaxies have large, underluminous mass at the center

End of Section