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Bit of Administration ….
• Reading
– BSNV Chaps. 9 and 15
• No Mathieu office hours today (Monday)!
• Additional observations for Lab 2, through April 5
– Due April 7 in lecture or April 9 at Mathieu office
• 12-week exam in two weeks - April 12, 7:15 pm
– Review session, Sunday, April 11, 6:30 pm
The Solar System
• A Sense of Scale
Around Earth
Around Europe
 0.1 
Distance to Moon
Distance to North America
The Solar System
• A Sense of Scale
The Solar System
• A Sense of Scale
The Solar System
• Inventory
• Sun
99.85% by mass
• Planets 0.1 % by mass
• Satellites and Rings
• Asteroids
• Comets
• Meteroids
• Dust
• Solar Wind (ionized gas)
The Solar System
• Inventory - “Sedna”
The Solar System
• General Characteristics of Major Planets - Dynamical
• Nearly circular orbits (Mercury and Mars most eccentric)
The Solar System
• General Characteristics of Major Planets - Dynamical
• Nearly circular orbits (Mercury and Mars most eccentric)
• All orbit within 10o of Earth’s orbital plane
The Solar System
• General Characteristics of Major Planets - Dynamical
• Nearly circular orbits (Mercury and Mars most eccentric)
• All orbit within 10o of Earth’s orbital plane
• All revolve in the same direction
• All rotate in the same direction (except Venus)
The Solar System
• General Characteristics of Major Planets - Radius
The Solar System
• General Characteristics of Major Planets - Age
• Earth - Oldest rocks 3.9 billion yr (4.5 billion yr inferred)
• Moon - 4.5 billion yr
• Meteorites - 4.6 billion yr
• Sun - 4.6 billion (theoretical)
• Universe - 12 billion yr
The Solar System
• General Characteristics of Major Planets - Physical Properties
Location
Size
Mass
Density
Appearance
Composition
Terrestrial
7 Giant Satellites
Jovian
Inner
Small (104 km)
0.1 - 1.0 MEarth
5 gm cm-3
Rock with craters,
volcanos
Heavy elements
Outer
Small (4000 km)
0.01 MEarth
2-3 gm cm-3
Rock, ice with craters,
volcanos
Heavy elements, ices
Outer
Large (105 km)
15 - 300 MEarth
1 gm cm-3
Gaseous, with
rock cores
Hydrogen, helium
Notes:
1) Densities: Rock = 3 gm cm-3, Water = 1 gm cm-3
2) Composition of Sun and Universe by numbers of atoms:
all else
Jupiter94% H, 6% He, 2%Saturn
Uranus
Mercury
Io
Venus Europa
Earth
Ganymede
Nepture
Mars
Callisto
The Formation of the Solar System
The Formation of the Solar System
• Interstellar Clouds
By Mass
• 73% Molecular Hydrogen
• 25%Atomic Helium
• 2% Dust (Metals)
ConcepTest!
The Taurus clouds are thought to be rather cold, with
temperatures of perhaps 30 K. If you wanted to test this
hypothesis by looking for light emitted by the Taurus clouds, in
what wavelength would you want to observe?
A) X-ray
B) Ultraviolet
C) Optical
D) Infrared
E) Radio
The Formation of the Solar System
• Dense Molecular Cores
(“Bok Globules”)
• ≈ 1 Mo
• ≈ 50,000 AU
• ≈ 10 oK
The Formation of the Solar System
The Formation of the Solar System
• Protoplanetary Disks
• ≈ 0.01 Mo
• ≈ 100 AU
• ≈ 3000 -> 10
oK
The Formation of the Solar System
The Formation of the Solar System
• Condensation Sequence
• Condensation Temperature
Temperature at which Solid
T > 50 oK
Gas
T > 200 oK
T > 1000 oK
Hydrogen (H)
Helium (He)
Gas
Gas
Gas
H20, Methane (CH4)
CO2, Ammonia (NH3)
Ice
Gas
Gas
Iron (Fe), Silicon (Si)
Metal Compounds
Rock
Rock
Gas
The Formation of the Solar System
• Condensation Sequence
M
1000 K
No Grains
V
Rock
Grains
E
M
J
200 K
Rock, Ice
Grains
The Formation of the Solar System
The Formation of the Solar System
• Grain Collisions ==> Planetesimals (100 km)
random
100 km
The Formation of the Solar System
• Planetesimal Accretion ==> Rocky Planets and Jovian Cores
gravity
The Formation of the Solar System
• Gas Accumulation ==> H and He onto Jovian Cores
gravity
Protomoons
ConcepTest!
Most comets have orbits that take them well beyond Jupiter. You
would expect their composition to be:
A) Rocks and heavy elements only
B) Rocks and ices only
C) Rocks, ices, and hydrogen and helium
The Formation of the Solar System
The Formation of the Solar System
• Dispersal of Hydrogen and Helium Gas
• Solar Wind?
• Jets?