1. 8. Solar System Origins Chemical composition of the galaxy
The solar nebula
Planetary accretion
Extrasolar planets

2. Our Galaxy’s Chemical Composition
Basic physical processes
“Big Bang” produced hydrogen & helium
Stellar processes produce heavier elements
Observed abundances
Hydrogen ~71% the mass of the Milky Way
Helium ~27% the mass of the Milky Way
Others ~ 2% the mass of the Milky Way
Elements as heavy as iron form in stellar interiors
Elements heavier than iron form in stellar deaths
Implications
A supernova “seeded” Solar System development
It provided abundant high-mass elements
It provided a strong compression mechanism

3. Solar System Chemical Composition

4. Coalescence of Planetesimals

5. Abundance of the Lighter Elements
Note: The Y-axis uses a logarithmic scale

6. The Solar Nebula Basic observation Basic implication
All planets orbit the Sun in the same direction
Extremely unlikely by pure chance
Basic implication
A slowly-rotating nebula became the Solar System
Its rate of rotation increased as its diameter decreased
Basic physical process
Kelvin-Helmholtz contraction Gravity  Pressure
As a nebula contracts, it rotates faster
Conservation of angular momentum Spinning skater
Kinetic energy is converted into heat energy
Accretion of mass increases pressure
Temperature & pressure enough to initiate nuclear fusion

7. Conservation of Angular Momentum

8. Formation of Any Solar System
Presence of a nebula (gas & dust cloud)
Typically ~ light year in diameter
Typically ~ 99% gas & ~1% dust
Typically ~ 10 kelvins temperature
A compression mechanism begins contraction
Solar wind from a nearby OB star association
Shock wave from a nearby supernova
Three prominent forces
Gravity Inversely proportional to d2
Tends to make the nebula contract & form a star
Pressure Directly proportional to TK
Tends to make the nebula expand & not form a star
Magnetism Briefly prominent in earliest stages

9. More Solar System Formation Stages
Central protostar forms first, then the planets
H begins fusing into He => Solar wind gets strong
This quickly blows remaining gas & dust away
Circumstellar disks
Many are observed in our part of the Milky Way
Overwhelming emphasis on stars like our Sun
Many appear as new stars with disks of gas & dust
Potentially dominant planets
Jupiter >2.5 the mass of all other planets combined
Many exoplanets are more massive than Jupiter
Knowledge is limited by present state of technology

10. The Birth of a Solar System

11. Formation of Planetary Systems

12. Planetary Accretion Basic physical process Critical factor
Countless tiny particles in nearly identical orbits
Extremely high probability of collisions
High energy impacts: Particles move farther apart
Low energy impacts: Particles stay gravitationally bound
Smaller particles become bigger particles
~109 asteroid-size planetesimals form by accretion
~102 Moon-size protoplanets form by accretion
~101 planet-size objects form by accretion
Critical factor
Impacts of larger objects generate more heat
Terrestrial protoplanets are [almost] completely molten
“Chemical” differentiation occurs
Lowest density materials rise to the surface Crust
Highest density materials sink to the center Core

13. Microscopic Electrostatic Accretion

14. Condensation Temperature
Basic physical process
Point source radiant energy flux from varies µ 1/D2
Ten times the distance One percent the energy flux
Any distant star is essentially a point source
The concept applies to all forming & existing stars
At some distance, it is cold enough for solids to form
This distance is relatively close for rocks
Much closer to the Sun than the planet Mercury
This distance is relatively far for ices
Slightly closer to the Sun than the planet Jupiter
This produces two types of planets
High density solid planets Terrestrial planets
Low density gaseous planets Jovian planets

15. Two Different Formation Processes

16. Condensation In the Solar System

17. The Center of the Orion Nebula

18. Mass Loss By a Young Star In Vela

19. Exoplanet Detection Methods

20. Extrasolar Planets: 13 Sept. 2002
Basic facts
No clear consensus regarding a definition
Usually only objects <13 MassJup & orbiting stars
Objects > 13 MassJup are considered “brown dwarfs”
Objects < 13 MassJup are considered anomalies
Orbiting a massive object fusing H into He
A star in its “normal lifetime”
Summary facts
88 extrasolar planetary systems
101 extrasolar planets
11 multiple–planet systems
Unusual twist
A few “planetary systems” may be “star spots”
Magnetic storms comparable to sunspots on our Sun

21. Exoplanets Confirmed by 2007
18 July 2003
117 extrasolar planets
102 extrasolar planetary systems
13 extrasolar multiple–planet systems
4 July 2005
161 extrasolar planets
137 extrasolar planetary systems
18 extrasolar multiple–planet systems
19 September 2007
252 extrasolar planets
145 extrasolar planetary systems
26 extrasolar multiple–planet systems

22. Extrasolar Planets Encyclopaedia
27 January 2010
429 planets
363 planetary systems
45 multiple planet systems 22

23. Extrasolar Planets: Size Distribution
MassJup

24. Most Recent Confirmed Exoplanets
29 January 2013
863 extrasolar planets
678 extrasolar planetary systems
129 extrasolar multiple–planet systems
2,233 unconfirmed Kepler candidates

25. Exoplanets: 17 September 2013

26. Exoplanets: Orbital Distribution

27. Exoplanets: Star Iron Content

28. Star Gliese 86: Radial Velocity Data
Doppler shift data reveal an extrasolar planet
An orbital period of ~ 15.8 days
A mass of ~ 5 . MJupiter

29. Possible First Exoplanet Photo

30. Important Concepts Galactic chemical composition
~98% hydrogen + helium
~ 2% all other elements
Solar System formation
Solar nebula
Compression mechanism
Gravity, pressure & magnetism
Protostar with circumstellar disk
Planetary accretion
Concept of condensation temperature
Rock & ices can form
Extrasolar planets
863 confirmed
2,233 Kepler candidates