3/3/2013

1

Formation of the Solar System H – 78%

He – 20%

O – 0.8%

C – 0.3%

N – 0.2%

Ne – 0.2%

Ni – 0.2%

Si – 0.06%

Fe – 0.04%

S – 0.04%

Etc.

Origins?

ISM – Interstellar Medium

Mainly in gas form

Molecules

~150 different molecules found

H2, CO, O2, H2O most common

NH3, CH4, HCN, CH3OH, H2CO, C2H5OH, NaCl

Form in gas, on surface of dust grains

Dust – 1% of ISM

3/3/2013

2

2 Atoms – AlCl, AlF, AlO, C2, CH, CH + , CN, CN + , CN -, CO, CO + , CF + , CP, CS, FeO, H2,

HF, HCl, KCl, NaCl, NH, N2, NO, NO + , NS, NaI, O2, OH + , HO, PN, PO, SO, SO + , SiC, SH,

SH + , SiN, SiO, SiS, MgH+

3 Atoms – AlNC, AlOH, C3, C2H, C2O, C2S, C2P, CO2, CO2+, H3

+, H2C, H2Cl+, HCO, HCO+,

HCP, HCS+, HOC+, H2O, H2O+, H2S, H2S

+, HCN, HNC, HNO, KCN, MgCN, MgNC, HN2+,

N2O, N2H+, NaCN, OCS, O3, SO2, c-SiC2, NH2, SiCN, SiNC

4 Atoms – CH3, c-C3H, l-C3H, C3N, C3N-, C3O, C3S, C2H2, HCCN, HCNO, HOCN, HCNH+,

HNCO, HNCS, HOCO+ , H2CO, H2CN, H2CN+ , H2CS, H3O+, HSCN, NH3, SiC3

5 Atoms - C5 C4H, C4H-, SiC4, l-H2C3, c-C3H2, CH4, HC3N, HCOOH, H2CNH, H2C2O, H2CCN,

SiH4 H2COH+, HCC-NC, NH2CN, HC(O)CN

6 Atoms - C5H, C2H4, CH3CN, CH3NC, CH3OH, CH3SH, HC3NH+, HC2CHO, HCONH2, l-

H2C4, c-H2C3O, C5N, HC4N, CH2CNH

7 Atoms - C6H, C6H-, CH2CHCN, CH3C2H, c-C2H4O, H3CNH2, H2CHCOH, HC4CN, CH3CHO

8 Atoms – H3CC2CN, H2COHCHO, HCOOCH3 CH3COOH C7H H2C6 CH2CHCHO,

CH2CCHCN, NH2CH2CN

9 Atoms - CH3C4H, CH3OCH3, CH3CH2CN, CH3CONH2, CH3CH2OH, HC7N, C8H, C8H-,

CH3CHCH2

10 Atoms - CH3C5N, (CH3)2CO, (CH2OH)2, CH3CH2CHO 11 Atoms – HC8CN, C2H5OCHO, CH3C6H, HCOC2H5

12 Atoms – C3H7CN, C6H6

13 Atoms - HC11N, HC10CN

24 Atoms – C14H10

60 Atoms – C60

70 Atoms – C70

Sources of ISM

AGB stars

Dust formation

3/3/2013

3

Formation Mechanism

Inward pull of gravity vs. gas pressure

• Jean’s Mass

MJeans=mass

, G =constants

m=mean molecular weight

1

T=Temperature

r=average density

rm

1

4

32/12/3

G

TMM Jeans

• Collapse happens quickly/slowly?

• Freefall time

Higher density – quicker collapse

Rotation rate, collapse rate multiple stars?

2/1

32

3

r

Gt ff

3/3/2013

4

• Theoretical collapse of cloud

– Energy lost (if transparent)

– Density increase (opacity increases)

– Temperature increase

– Deuterium fusion (1 million K)

• Slow down

– Further contraction

– Heating of proto-star heats cloud

• Long IR at first

• Short IR later

• Reality?

Bok Globules

3/3/2013

5

• Star formation buried in Cocoon Nebula

– Cloud of gas/dust (100:1)

– Few 100 AU in size

– Strong IR source

• Observations

– R Mon & other IR stars

– Proplyds (proto-planetary disks)

• Observed in Orion nebula, Carina nebulae, etc.

• <1 million years old

R Mon T Tauri

3/3/2013

6

3/3/2013

7

H-H Objects

• Outflows of material

• Observed near Bok globules

• 400 exist

• ½ pc from source star

• 100 – 1000 km/s

later on…

• Collapse of cloud material – In disk around proto-star

– Eventually becomes transparent (after formation of larger particles)

• Star formation finishes up during T Tauri stage – Bright (large radius)

– Fast rotation

– Found near nebulae

– IR excess

– Strong magnetic fields*, large sun/star spots

– Lasts ~100 million years (limits planet formation)

– Excess of Li - young

3/3/2013

8

What about forming planets?

Look at the disks

Several hundred AU in size Kuiper belt

Composition Comet

Gap in inner part (cleaned out)

Mass ~ 0.001 – 0.1 M

Some ring-like

Beta Pictoris – 1500 AU wide

3/3/2013

9

3/3/2013

10

• Disk Material

– Distribution depends on angular momentum

– Infall heats disk up

1500 K near 1 AU

100 K near 10 AU

– Temperature gradient Energy transport

• Convection ( to disk)

• Turbulence (radially)

• Composition distribution (limited)

• Now you’re ready to make a planet! Or two.

Planet Formation

• When did it happen?

– When the planets formed?

– When the material formed?

• Radiometric dating (isotope )

– Many short lived radioactive elements

• 41Ca (0.15 Myr), 26Al (1.1 Myr), 60Fe (2.2 Myr), 53Mn (5.3 Myr), 107Pd (9.4 Myr), 182Hf (13 Myr), 129I (23 Myr), etc.

• Source? – Large star (Supernova, Evolved supergiant)

– Spallation

• Chemical distribution – how’d that happen?

– Example: Oxygen

• Gas: O2, CO, CO2, H2O, etc.

• Liquid/solid: H2O, CO2, etc.

• Solids: Silicates, ferrous oxide, olivine, serpentine, etc.

• Definitions: Minerals & Rocks

– Mineral – what’s that?

• Examples?

– Rock – what’s that?

• Examples?

3/3/2013

11

Minerals

• Several different groups –

– Silicates (Si, O)

• On Earth ~95% are silicates

• Common silicates – Silica: Quartz

– Feldspars: Orthoclase feldspars, Plagioclase feldspars

– Pyroxenes

– Amphiboles

– Micas

– Olivines (tend to sink)

Non-silicates

Such as

– Oxides

• Usually Fe+O:

Magnetite, hematite, limonite (Mars)

Ilmenite, Armalcolite (Moon’s maria)

– Pyrite (FeS2), Troilite (FeS) – in cores

– Clay minerals – hydrous aluminum silicates

Outer solar system

– Carbonaceous minerals: graphite, carbon rich

– Ices: Water, CO2, NH3, CH4

Rocks

• Three types

– Igneous

• Lavas

• Basaltic

• Grantitic

• Andesite

• Anorthosite

• Obsidian

3/3/2013

12

• Sedimentary – atmosphere/hydrosphere/crust

– Weathering of rocks

• Chemical

• Mechanical

– Transport

– Layering, settling

Types:

• Shale

• Sandstone

• Limestone

• Dolomite

• Evaporites (halite, gypsum)

• Metamorphic

– Altering, re-crystallization

• Pressure

• Temperature

• Chemistry

– Examples:

• Marble

• Quartzite

• Gneiss

• Schist

• Slate

• Shocked quartz

• Metamorphic

– Altering, re-crystallization

• Pressure

• Temperature

• Chemistry

– Examples:

• Marble

• Quartzite

• Gneiss

• Schist

• Slate

• Shocked quartz

3/3/2013

13

• Mineral evolution – depends on location

– Temperature

– Pressure

– Interactions available (other elements/minerals)

• Ex: formation of CO depletes not only C, but also O

• Remember the starting situation:

– H, He, O, C, N, etc.

– H, He not common in planets (in terms of ratio)

– Other abnormalities need to be explained

• T>2000 K – Everything evaporated, no formation

• T ~ 1700 K – REE, oxides of Al, Ca, Ti form

• Corundum (Al2O3)

• Perovskite (CaTiO3)

• Spinel (MgAl2O4)

• T ~ 1400 K – Iron – Nickel alloy forms

• T < 1400 K – Magnesium silicates form

• Forsterite (Mg2 SiO4)

• Enstatite (MgSiO33)

3/3/2013

14

• T < 1200 K

– Feldspars start to appear

– First are plagioclase anorthite (CaAl2Si2O8)

– Later (T~ 1000 K) sodium and potassium feldspars ((Na, K)AlSi3O8)

• T ~ 700 K

– Iron, H2S react, form troilite (FeS)

• T ~ 500

– Iron, water react, form iron oxide

(Fe+H2O FeO+H2)

Iron oxide reacts with enstatite, forsterite form olivines ((Mg, Fe)2SiO4), pyroxenes ((Mg,Fe)SiO3)

• T < 500 K

– Water major player (gas)

– Reacts with olivines, pyroxenes to form hydrated silicates

• Serpentine Mg6Si4O10(OH)8

• Talc Mg3Si4O10(OH)2

• Tremolite Ca2Mg5Si8O22(OH)2

• Hydroxides like Brucite Mg(OH)2

• T < 200 K

– Water ice forms (mineral)

– Cooler temperatures

• Ammonia, methane condense as hydrates, clathrates

• Below 60 K

– CO, N2 form clathrates with H2O ice

• Below 40 K

– CH4, Ar ices form

• Below 25 K

– CO, N2 form ices

Exceptions – find high temperature minerals inside of low temperature structures (carbon rich meteorites). Requires migration.

Temperature structure changes over time

3/3/2013

15

Let’s make some planets

• Minerals formed – what’s next?

• Particles must come together safely

– Why?

– How?

• Corpuscular dragging

• Electrostatic forces

• Gravitational perturbations

• Safe when they are planetismals

– 0.001 m – 1000’s of meters

– Grow via collisions

Growth depends on

– Density

– Relative velocities

At 1 AU, and Earth forms in 107 – 108 years

(most growth early on)

Further out, density lower, growth rates slower.

At 5 AU, takes 108 years to form Jupiter

Uh-oh!

Too late!

T Tauri will destroy it!

Need to speed up growth rates.

3/3/2013

16

Runaway growth mechanism

Requires relative velocities < escape velocities

Limits region of growth

Can extend beyond Hill sphere

Perturbations, gas drag also help

Terrestrial Formation • Heating up

– Collisions, Radioactive decay, Gravitational, Chemical processes

• Energy lost

• Energy transport – Convection vs Conduction

• Primitive Atmosphere – H2O CO2

• Surface melting (M ~ 0.2 M, T~1600 K)

• Atmosphere evolution

– Loss of light-weight gases

– Impacts, outgassing

Gas Giant Formation

• Quick formation (~107 years)

• Core formation first (similar to terrestrial)

• M ~ 10-20 M, gas infall significant

• Eventually reach runaway accretion

• Fills Hill sphere (100’s x current size)

• Contraction (fast then slow) ~10,000 years

• Heating – convection

• Temperature, Luminosity (IR) stabilize

3/3/2013

17

Ice Giant Formation

• Similar to gas giant (but more heavy elements)

• Cores less massive (less material)

• No runaway

• Contraction ends after 200,000 years

Loose Ends

• Asteroid belt

– Not a planet (too little mass)

– Formerly more objects there

– Jupiter’s influence

– Formed in current location

• Cometary masses

– Formed between 3-30 AU

– Ejected by Gas/Ice giants (mainly Jupiter)

– Migration of Jupiter inwards, other giants outward

• Satellites

– Similar to solar system formation scenario

– Regular (Normal) satellites:

• Found near equatorial plane of planet

• Prograde orbit, rotations, low eccentricity, inclination

• Formed with planet

– Irregular (Captured) satellites:

• Random orientations, orbits, motions, retrograde

• Formed elsewhere – ice/rock, ice composition

– Collision satellites:

• Earth-Moon, Pluto system, Asteroids

• “Chip off the old block”

3/3/2013

18

• Rings

– Not primordial

– Short lived structures

– Composition peculiarities

– Fed by external sources, local sources

HD 100546

3/3/2013

19