HNRS 227 Lecture #16 & 17Chapters 12 and 13

The Universe and Solar Systempresented by Prof. Geller21 and 23 October 2003

Key Points of Chapter 12

Historical Views geocentric model of the universe

Ptolemaic Model

heliocentric model of the universeCopernican Model

Coordinate Systems Local Horizon System

altitude, azimuth

Celestial Coordinate Systemright ascension, declination

Key Points of Chapter 12

Measurements angular degrees

1 degree = 60 minutes = 3600 seconds

hour-angleone hour is 15 degrees of arc

light yeardistance traveled by light in a year

Astronomical Unit (AU)mean distance of Earth to Sun

Key Points of Chapter 12

Main Sequence Stars core, radiation zone, convection zone,

photosphereMagnitude Scale

log scale lower value brighter (x 2.5) than higher

value absolute versus apparent

absolute is magnitude at 10 parsecs

Key Points of Chapter 12

Temperature of stars Wien’s Law spectral classes based upon

temperaturenot linear scale

H-R Diagram temperature versus absolute brightness following the evolution of stars

The Hertzsprung-Russell (HR) Diagram

The Life Story of Stars

Thermal Thermal EnergyEnergy

Weight of outer layersWeight of outer layers

Gas Gas PressurePressure

GravityGravity

SurfaceSurface

CenterCenter

LuminosityLuminosity Gravity squeezes Pressure forces resist

Kinetic pressure of hot gases Repulsion from Pauli exclusion

principle for electrons - white dwarf Repulsion from Pauli exclusion

principle for neutrons - neutron star

None equal to gravity - black hole Energy loss decreases

pressure Energy generation replaces

losses Star is “dead” when energy

generation stops White dwarf, neutron star, black

hole

Post Main Sequence Evolution

Helium burning

Heium “Burning”Heium “Burning”

44HeHe22 + + 44HeHe2 2 88BeBe44

88BeBe44 + + 44HeHe2 2 1212CC66 + +

1212CC66 + + 44HeHe2 2 1616CC88 + +

Evolution from Giants to Dwarfs

Stellar Evolution by Mass

100100 0.10.10.40.41.01.04.04.010104040Mass (MMass (MSunSun = 1) = 1)

White dwarfsWhite dwarfs

NsNsBlack holesBlack holes

Main sequence starsMain sequence stars

Heavy nuclei fusionHeavy nuclei fusion

SupernovaeSupernovae Planetary nebulaePlanetary nebulae

C detonationC detonation

Helium flashHelium flash

Supergiants GiantsSupergiants Giants

25 Msun Star EvolutionSSttaaggee CCeennttrraall

TTeemmppeerraattuurree((KK))

CCeennttrraallDDeennssiittyy((gg//ccmm33))

DDuurraattiioonn ooffssttaaggee

Hydrogen burning 4 x 107 5 7 x106 year

Helium burning 2 x 108 7 x 102 5 x105 year

Carbon burning 6 x 108 2 x 105 600 year

Neon burning 1.2 x 109 4 x 106 1 year

Oxygen burning 1.5 x 109 1 x 107 6 months

Silicon burning 2.7 x 109 3 x 107 1 day

Core collapse 5.4 x 109 3 x 109 0.2 seconds

Core bounce 2.3 x 1010 4 x 1014 milliseconds

Explosion About 109 Varies 10 seconds

Key Points of Chapter 12

Galaxies our own Milky Way different types

elliptical, spiral, barred spiral

Hubble’s LawCosmology

Recall the Doppler Shift

A change in measured frequency caused by the motion of the observer or the source classical example of pitch of train

coming towards you and moving away

Hubble’s Law

The further away a galaxy is, the greater its recessional velocity and the greater its spectral red shift

Hubble’s Conculsion

From Hubble’s Law we can calculate a time in the past when universe was a point

Big bang occurred about 15 billion years ago big bang first proposed by George Gamow

based upon such evidence big bang named by antagonist Fred Hoyle

who preferred the steady-state model

Big Bang Summary

Era Epochs Main Event Time after bang

The Vacuum Era Planck EpochInflationary Epoch

QuantumfluctuationInflation

<10-43 sec.<10-10 sec.

The Radiation Era Electroweak EpochStrong EpochDecoupling

Formation ofleptons, bosons,hydrogen, heliumand deuterium

10-10 sec.10-4 sec.1 sec. - 1 month

The Matter Era Galaxy EpochStellar Epoch

Galaxy formationStellar birth

1-2 billion years2-15 billion years

The DegenerateDark Era

Dead Star EpochBlack Hole Epoch

Death of starsBlack holesengulf?

20-100 billion yrs.100 billion - ????

Key Points of Chapter 13(some of which was eliminated)

Geocentric solar system Ptolemaic model

Heliocentric solar system Copernican model

Kepler’s Laws of Planetary MotionOrigin of Solar SystemOverview of Planets

Kepler’s Laws of Planetary Motion

Kepler’s First Law of Planetary Motion planets orbit sun in an ellipse with sun at

one fociKepler’s Second Law of Planetary Motion

planets sweep out equal areas in equal timestravel faster when closer, slower when farther

Kepler’s Third Law of Planetary Motion orbital period squared is proportional to

semi-major axis cubed•P2 = a3

Planetary Observations

Planets formed at same time as SunPlanetary and satellite/ring systems

are similar to remnants of dusty disks such as that seen about stars being born

Planet composition dependent upon where it formed in solar system

Other Planet Observations

Terrestrial planets are closer to sun Mercury Venus Earth Mars

Jovian planets furthest from sun Jupiter Saturn Uranus Neptune

Other Observations

Radioactive dating of solar system rocks Earth ~ 4 billion years Moon ~4.5 billion years Meteorites ~4.6 billion years

Most orbital and rotation planes confined to ecliptic plane with counterclockwise motion

Extensive satellite and rings around JoviansPlanets have more of the heavier elements

than the sun

A Linear View of AbundanceLinear Plot of Chemical Abundance

0

10000

20000

30000

40000

50000

60000

70000

80000

90000

100000

H He C N O Ne Mg Si Si Fe

Chemical Species

Rel

ativ

e ab

un

dan

ce

Log Abundance of ElementsLogarithmic Plot of Chemical Abundance of Elements

1

10

100

1000

10000

100000

H He C N O Ne Mg Si Si Fe

Chemical Species

Rel

ativ

e A

bu

nd

ance

Planetary Summary

PlanetMass

(Earth=1)Density(g/ cm3)

MajorConstituents

MercuryVenusEarthMars

0.060.821.000.11

5.45.25.53.9

Rock, IronRock, IronRock, IronRock, Iron

JupiterSaturn

31895

1.30.7

H, HeH, He

UranusNeptune

1417

1.31.7

Ices, H, HeIces, H, He

Nebular Condensation (protoplanet) Model

Most remnant heat from collapse retained near center

After sun ignites, remaining dust reaches an equilibrium temperature

Different densities of the planets are explained by condensation temperatures

Nebular dust temperature increases to center of nebula

Nebular Condensation Physics

Energy absorbed per unit area from sun = energy emitted as thermal radiator

Solar Flux = Lum (Sun) / 4 x distance2

Flux emitted = constant x T4 [Stefan-Boltzmann]

Concluding from above yields

T = constant / distance0.5

Nebular Condensation Chemistry

Molecule Freezing Point Distance fromCenter

H2 10 K >100 AUH2O 273 K >10 AUCH4 35 K >35 AUNH3 190 K >8 AU

FeSO4 700 K >1 AUSiO4 1000 K >0.5 AU

Key Points of Chapter 13(some of which was deleted)

Earth’s Motions revolution

about Sun

rotationon its axis

Reason for the seasons tilt of the Earth’s axis

Measuring time hours, minutes, seconds

Key Points of Chapter 13(all eliminated from 2nd edition)

The Moon phases of the Moon Eclipses

lunarsolar