Solar System

• Read Your Textbook: Introduction to Physical Science– Chapter 20 – Chapter 21-26

• Answer Questions– Chapter 20: Q4;P1,4,6,9 W3– Chapter 21: Q2,5-8 P2,3 W3– Chapter 22: Q1-3,12;P2,3,7 W1,4– Chapter 23: Q2,4,6,9 W1

Solar System ScaleThe Sun has 99.85 % of the mass of the solar system

Jupiter has 2/3 of the remaining that formed planets

Planetary Orbital InclinationOur Solar System is Very Nearly Disk Shaped

Angles of the planets orbits are shown with respect to the

ecliptic (earth-sun orbit).

Planetary Densities

moon

• Terrestrial (Earth-Like) Planets– High Densities (mostly metals and solids)– Small sizes– Near the Sun

• Jovian (Jupiter-Like) Planets– Low Average Densities (mostly gases and ices)– Large sizes– Far from the Sun

Two Planet Types

• Terrestrial Rock Samples (Greenland, Canada, Australia)– 3.9 billion years

• Lunar Rock Samples (Apollo Missions)– 4.1 billion years

• Meteorite Samples– 4.5 billion years

• Solar modeling

• The solar system is roughly 4.5-5.0 billion years old.

Ages Determined

Solar Nebula TheoryA complete description of the formation of the solar system

must explain the observed characteristics:

Disk-like NatureA complete description of the formation of the solar system

must explain the observed characteristics:• The disk shape nature of the solar system

– All planets orbit within 10 degrees of the Earth-Sun orbit – Common Rotations and Revolutions

Density VariationsA complete description of the formation of the solar system

must explain the observed characteristics:• The disk shape nature of the solar system

– All planets orbit within 10 degrees of the Earth-Sun orbit – Common Rotations and Revolutions

• Terrestrial (Earth-Like) Planets– high density, rocky, small, close to the sun

• Jovian (Jupiter-Like) Planets– low density, gaseous, large, farther away from the sun

Common AgeA complete description of the formation of the solar system

must explain the observed characteristics:• The disk shape nature of the solar system

– All planets orbit within 10 degrees of the Earth-Sun orbit – Common Rotations and Revolutions

• Terrestrial (Earth-Like) Planets– high density, rocky, small, close to the sun

• Jovian (Jupiter-Like) Planets– low density, gaseous, large, farther away from the sun

• Common Ages• Space Debris

– asteroids, comets, ring systems

OrionStar formation

region

in the

constellation

of Orion

visible to

the unaided

eye.

Star Formation RegionsBelt and Sword of Orion

Orion Nebula & Horse Head Nebula

NebulosityHot new stars illuminate the gas and dust of the horse head

nebulae in Orion

Infant StarsOrion Nebula Trapezium

Stellar Nurseries• New, Young stars are associated with gas and dust.

Eagle Nebula

A Star is Born

Proto-StarsThe Orion Trapezium Region in Infra-Red Light

Angular Momentum ConservationThe ice skater, the ballerina, the earth’s rotation and a child’s

top, believe it or not, all have a lot to do with each other, and

the formation of the solar system.

• Angular Momentum:– Rotating Objects Have It– They Want To Conserve It

• Depends on Mass• Depends on velocity

• Depends on Distribution of Matter About the Rotation Axis

Sphere To DiskWhen a spherical proto-stellar cloud begins collapsing,

it has some inherent rotation (and thus angular momentum)

associated with it. As material moves to smaller radii,

the rotation increases, like the ice skater and ballerina

in a spin bringing their arms in toward the

rotational axis.

Material along the axis does not spin as much as material

near the “equator” and so does not have as much angular

momentum to save. Therefore, the material at the poles

falls closer to the center.

RotationGravitationally collapsing rotating spheres tend to create

flattened spinning disks.

The inner parts of the disk rotate faster than the outer parts.

Solar NebulaSolar

System

Formation

Proto-Stellar DiskRadiation from the new star,

tries to escape.

The infalling disk material

absorbs it and cuts it off.

Its only escape is along the

poles of rotation where

the disk is thinner.

Eta Carina

PictorisDisk

material

around

other

stars.

Proto-Stellar Accretion Disk• Bi-Polar Outflow

Planetary OrbitsKEPLER'S III LAW:

THE RELATION BETWEEN ORBITAL PERIOD P (years) AND

AVERAGE DISTANCE a (A.U.) IS A CONSTANT FOR THE SOLAR SYSTEM P2/a3 = constant

Planetesimal CoalescenceEddies,

whirlpools,

and other

density variations

cause

planetesimals

which later

accrete and

collide to

form into

the planets.

Proto-planet Accretion & Coalescence

• N-body Coalescence

Planetary Densities

Condensation TemperatureTemperature decreases with distance from the sun.

Tem

pera

ture

(K

)

500

750

1000

1500

2000

Distance (Astronomical Units A.U.)

0.1 0.5 1.0 5.0 10.0 40.0Mercury

EarthJupiter Saturn Pluto

Metal Oxides

Metallic Iron and Nickel

Silicates

Sulfides

Water IceAmmonia and Methane Ices

Solids and DensityDensity decreases with distance from the sun also in the

same way that the temperature does. Only matter with

higher density, existed as solids (not gas) at the higher

temperatures found near the proto-sun.

Distance (Astronomical Units A.U.)

Tem

pera

ture

(K

)

500

750

1000

1500

2000

0.1 0.5 1.0 5.0 10.0 40.0Mercury

EarthJupiter Saturn Pluto

Metal Oxides

Metallic Iron and Nickel

Silicates

Sulfides

Water IceAmmonia and Methane Ices

Solar Nebula Composition• The denser materials are able to exist as solids at higher temperatures. The only solids found in the inner portions of the solar nebula are the dense metals that form the rocky terrestrial planets.

• This dense material also exists at large radii from the proto-sun.

• Less dense ices only exist in the outer solar nebula.

Pressure Balancing GravityWhen the star

begins generating

energy within,

radiation and gas

pressure build up

to counteract

gravity.

Radiation and winds

move outward,

away from the star.

Density EvolutionThe initial distribution of material in the solar nebula (A) changes, as

the sun accretes material and finally “turns ON” (B), and material is

blown out of the interior (C).

Den

sity

(g/

cm3 )

Distance (Astronomical Units A.U.)

0.1 0.5 1.0 5.0 10.0 40.0Mercury

EarthJupiter Saturn Pluto

A

B

C

Terrestrials versus Jovian Planets• Terrestrial planets formed from the materials that could exist at the highest temperatures. They are higher density rocky bodies close to the proto-sun.

• Jovian planets formed from both high density and the much more abundant low density material that was able to exist as solids far from the proto-sun. There was much more material to draw from (both metals and ices) as compared to material the terrestrial planets had available. Therefore, the jovian planets are less dense and farther from the sun.

• Why are the Jovian planets so much larger?

Clearing the Inner Disk• Once the Sun had “turned-ON”, the material in the inner disk was blown clear, thus truncating the accretion and coalescence processes of the terrestrial planets. Their growth was “stunted” by the birth of our Sun.

• The jovian planets were able to draw on the metals and much more abundant ices and grew very large.

• Jupiter is the largest planet probably because:– It is the nearest “far” planet (existed in a higher density region) – More numerous ices could also be accreted as well as metals– Not stunted by clearing of the inner disk (may have benefited)

Are We Unique?• Solar Nebula Theory Explains

– The disk shape nature of the solar system, including orbits– Existence of Terrestrial Planets– Existence of Jovian Planets– Common Ages (Everything Formed At Once)– Space Debris (Left Over Junk)– Planets form as a by-product of star formation

• Solar Nebula Theory Predicts– Accretion disks should be found around young stellar systems– Planets form as a by-product of star formation– Terrestrials close, Jovians far, and a large “Jupiter” in the middle

• The sky should be full of solar systems of similar nature!