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Modern
Planetology
Printable
version
February
17, 2000
Announcements
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QUIZ
NEXT WEEK IN DISCUSSION SECTION
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Covers
chapters 1-6
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Most
problems multiple choice test problems
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A few
like those on homework
Observing
the entire electromagnetic spectrum
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Recall that visible light
is only a tiny portion of the electromagnetic spectrum
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Special telescopes are needed
to observe at other wavelengths
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Radio--metal
dishes
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Infrared and UV--optical
telescopes with special detectors above the atmosphere
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X-ray--grazing
incidence optics, CCDs, above the atmosphere
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Gamma-Rays--no optics, only
special detectors
Text
Figure 5-7: Electromagnetic Spectrum
VLA
image (Radio)
IRAS
(Infrared)
Cerro
Tololo (Optical)
IUE
(Ultraviolet)
Hubble
(Near IR, Optical, Ultraviolet)
Chandra
image (X-ray)
X-ray
Mirrors
GRO
(Gamma Ray Observatory)
NASA's
Great Observatories
The
Spectrograph
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most
of the information we know about the planets comes from spectrographs
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a spectrum
is worth a thousand pictures
Prism
Spectrograph
Grating
Spectrograph
Quick
Course Review
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Scientific Method
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Seasons, Motion of Stars
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Moon's orbit
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Heliocentric solar system
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Electromagnetic Radiation
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Telescopes
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Modern
Planetology
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Formation
of the Solar System
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Earth
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Moon
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Midterm
Solar
System Overview
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Two types of planets: Terrestrial
and Jovian
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Terrestrial
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Jovian
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Other: Pluto
Textbook
Figure 7-2: The planets (not to scale)
Orbital
Characteristics of the Planets
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Terrestrial
planets close to the Sun
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Jovian
planets far from the Sun
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Pluto
is somewhat different
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The
solar system is HUGE compared to the planets
Textbook
Figure 7-1: planet orbits (to scale)
Physical
Characteristics of Planets
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Terrestrial planets are rocky
with thin atmospheres
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Jovian planets are gaseous
with a rocky core
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much bigger than terrestrial
planets
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Pluto is rock and ice
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There is a physical mechanism
for this division (next lecture)
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Note typo in box 7-1 of text:
Average
density is total mass divided by total VOLUME
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Water density is 1000 (kg/m3)
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Saturn would float in water
Textbook
Figure 7-3: The Sun and the Planets to Scale
Moons
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All
the planets except Mercury and Venus have moons
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More
than 50 moons total
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Only
7 big ones
| Satellite |
Parent |
Diameter |
Av Density |
|
Planet |
(km) |
(kg/m3) |
| Moon |
Earth |
3476 |
3340 |
| Io |
Jupiter |
3630 |
3570 |
| Europa |
Jupiter |
3138 |
3020 |
| Ganymede |
Jupiter |
5262 |
1940 |
| Callisto |
Jupiter |
4800 |
1860 |
| Titan |
Saturn |
5150 |
1880 |
| Triton |
Neptune |
2700 |
2070 |
Textbook
Figure 7-4: Moons compared to Mercury
A
Spectrum is worth 1000 pictures
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Spectral
lines reveal:
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Chemical
composition
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Temperature
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Relative
speed
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Examples
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Saturn's
moon Titan has methane (CH4)
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Europa
has water ice
Textbook
Figure 7-5b: Titan reflection geometry
Textbook
Figure 7-5a: Titan spectrum
Textbook
Figure 7-6: Europa Spectrum
Chemical
Compositions of Planets
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Jovian planets are mostly
Hydrogen and Helium (gasses)
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Terrestrial planets are mostly
heavy elements like:
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Iron (Fe)
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Silicon (Si)
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Magnesium (Mg)
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Sulfur (S)
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Nickel (Ni)
Textbook
Figure in Box 5-4: Periodic table
Textbook
Figures 7-7 and 7-8: Jupiter and Mars
Terrestrial/Jovian
Division Not an Accident
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All planets have a rocky
core
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Planets close to the Sun
are warmer
| Planet |
K |
oC |
oF |
| Mercury |
600 |
327 |
621 |
| Mars |
300 |
27 |
81 |
| Jupiter |
150 |
-123 |
-189 |
| Neptune |
63 |
-210 |
-346 |
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Hot atoms and molecules move
faster than cold ones (phases of matter)
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solids--molecules/atoms locked
in
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liquids--molecules/atoms
loosely associated
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gas--each molecule/atom independent
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plasma--atoms knocking the
electrons out of each other
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Gas molecules/atoms are acted
upon by gravity
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Heavy gasses like CO2
(carbon dioxide) or CH4 (methane) can stick to small planets/moons
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Light gasses like H2
(hydrogen) and He (helium) escape
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Light gasses stick to Jovian
planets
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Atmosphere composition
influenced by temperature, gravity
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Example: water
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Water on Mercury boils--gas
(water vapor)
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Most water on Earth is liquid
(oceans)
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Water in the Jovian planets/moons
is ice
Textbook
Figures 7-7 and 7-8: Jupiter and Mars