Solar System Overview
Facts about our Planetary System
Goals & Outcomes
• Learn some simple astronomical nomenclature/terminology.
• Learn about some problems astronomers and astrophysicists
are trying to solve, and understand the methods scientists are
using to try to solve these problems
• Develop a sense of what scientists know about the overall
universe, its constituents, and our location
• Understand the link between the composition and location of
the constituents in the solar system
• Compare the characteristics of the planets and major moons of
the Solar System
• Compare and contrast the terrestrial, jovian, and uranian
planets.
• Explain the climatic conditions of the inner planets
Sun
• 99.9% of solar system’s mass
• 70% Hydrogen, 28% Helium, 2% other
– Universe: 75% H, 23% He, 2% other
• Fusion powered: 4H  1 He + energy
– Fuses 600 megatons H into 596 Mton He each sec.
• Sunlight  most warmth & light in solar system
• Solar wind comes off the Sun.
– Charged particles, fast.
– Causes Northern/Southern Lights
• aurora borealis/australis
– Affect atmospheres, electronics, magnetism
• Sun rotates counterclockwise
Sun
The picture shown to the
right is taken using the
Hydrogen 3  2 transition
(red colored, called H-alpha
Solar System (cont)
•
•
•
•
The Sun is 99.9% of the solar system.
Everything else is tiny.
“Leftovers”
If we were really learning the solar system,
you’d only learn about the Sun!
Finding patterns
See also page 210
• Examine motions of the planets to look for
trends. We’ll examine 3 properties:
– Orbit tilt = “inclination”
– Planet’s rotation tilt
– Eccentricity (squished-ness of orbit)
• In graphs that follow, I called the Moon
“planet” 3.5 because it’s like the inner
planets.
• The book left Pluto out. I put Pluto in these
graphs so you can see why Pluto is no
longer a planet.
California Elementary School
Science Standards for solar system
•
From California Science Standards, grade 5
– Students know the Sun, an average star, is
the central and largest body in the solar
system and is composed primarily of
hydrogen and helium.
– Students know the solar system includes
the planet Earth, the Moon, the Sun,
eight other planets and their satellites,
and smaller objects, such as asteroids
and comets.
•
Satellites = moons
California Elementary School
Science Standards for solar system
•
And from the high school standards:
–
–
–
–
Students know the evidence indicating that the planets
are much closer to Earth than the stars are.
Students know the Sun is a typical star and is
powered by nuclear reactions, primarily the
fusion of hydrogen to form helium.
Students know the solar system is located in an outer edge
of the disc-shaped Milky Way galaxy, which spans 100,000
light years.
Students know galaxies are made of billions of stars and
comprise most of the visible mass of the universe.
•
Not true anymore. Most visible mass seems to be located in the
center of galaxy clusters.
Inclination of orbits
• Pattern
• Exceptions
Orbit tilt relative to Earth
(degrees)
• Implication
Planet orbit inclination
20.0
15.0
10.0
5.0
0.0
0
1
2
3
4
5
6
Planet Number
7
8
9
10
Tilts of planets
• Pattern
Planet's Tilt
• Implication
Tilt (degrees)
• Exceptions
200.0
150.0
100.0
50.0
0.0
0
1
2
3
4
5
6
Planet Number
7
8
9
10
Orbit Eccentricity (how elliptical)
• Pattern
• Implication
• Exceptions
Eccentricity (0 = circle)
Planet Eccentricity
0.3
0.25
0.2
0.15
0.1
0.05
0
0
1
2
3
4
5
6
Planet Number
7
8
9
10
Summary of Motions (p. 212)
• Orbits – most are nearly circular
• Orbit Directions – counterclockwise, most in the same
disk (small “inclination”)
• Rotations – also counterclockwise, also in the same
disk as orbits (small tilt)
• Most moons’ orbits line up with planets’ rotation
• Motions are very organized. What does that tell us?
– Clues about how solar system formed
• What about Pluto?
• More clues come from planets…
Finding patterns
• Examine characteristics of the planets to look
for trends.
– Location
• Further planets should be …
– Size
– Density
– Reflectivity (albedo)
• We’ll discuss other traits with a long table.
• Start with location: pages 210-211, or bottom
of any page: 214-223. What do you see?
Temperatures & distances
Predictions based
on the distance to
the Sun.
Planet Temperatures
Predicted Average Temperatures
• Pattern
800
Venus is almost the same temp day &
night
Temperature (K)
700
• Implication
600
Day Temp
only
500
400
300
Day/night
Middle Temp
Night
only
200
100
• Exceptions
Observed daytime temperatures
0
0
1
2
3
4
5
6
Planet Number
7
8
9
10
Sizes – radius
• Pattern
Planet Radius
80000
• Implication
Radius (km)
70000
60000
50000
40000
30000
20000
10000
• Exceptions
0
1
2
3
3.5
4
5
Planet Number
6
7
8
9
Sizes -- Mass
• Pattern
• Exceptions
Planet Mass (Earth = 1)
• Implication
Planet Masses
1000.000
100.000
10.000
1.000
0.100
0.010
0.001
0
1
2
3
4
5
6
Planet Number
7
8
9
10
Densities of planets (what is density?)
Planet Density
• Pattern
• Implication
Density (g/cc)
6
5
4
3
2
1
• Exceptions
0
1
2
3
3.5
4
5
Planet Number
6
7
8
9
Reflectivity (Albedo)
• Pattern
Planet Reflectivity (Albedo)
Percent
• Implication
• Exceptions
70%
60%
50%
40%
30%
20%
10%
0%
0
1
2
3
4
5
6
Planet Number
7
8
9
10
Planet characteristics
• Here comes the long chart
• Summary of the major trends / differences
2 types of planets
Characteristic
Location
(see also pages 224-225)
Terrestrial
Jovian
Far from Sun
Cold
Far apart
Large
Outside composition
Close to the Sun
Warm
Close together
Small
Rocky
Interior
Metallic
Very compressed – liquid
and/or metallic, solid core
Density
Dense
Low density
Small, solid, close together,
located where it’s warm
Large, H & He, far apart,
located where it’s cold
Temperature
Spacing
Size & mass
Summary
Gas (hydrogen, helium,
water, ammonia, methane)
Moons
No “traditional” moons Many moons
Rings
Magnetic field
None
Weak
All have rings
Strong
Rotation rate
Slower (than 24 hrs)
Faster (10-17 hrs)
Calif. Elementary School Science
Standards for atmospheres
•
From California Science Standards,
grade 5
– Students know that the Earth's
atmosphere exerts a pressure that
decreases with distance above
Earth's surface and that at any point it exerts
this pressure equally in all directions.
•
So pressure INCREASES with
depth.
Terrestrial planets
All “nine” planets
Sun & planets
Asteroids, Meteoroids, and Comets
Leftovers
• Asteroids – rocky, smaller than big moons.
– Radius = few hundred km or less
– Most in the asteroid belt
• Between Mars and Jupiter
• Meteoroids – small rocks in space
– Too small to be called asteroids
– Meteors – meteoroid hitting Earth
• Also called: shooting stars, falling stars. They’re NOT stars!
– Meteorite – meteor that hits the ground
• Comets – icy with rocks
– Frozen except when _______________.
– Tails only when close to Sun. Always point away from Sun
– Two locations: beyond Neptune (Kuiper) & far far away (Oort)
• WHY:
leftovers
gravitationally ejected
The Cheetos in the bag I passed
around are called “asteroids.” What
should they be called?
1. Asteroids
2. Meteoroids
3. Comets
0
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
Brief History of Solar System
formation
• Based on the patterns we saw…
• Orbits & rotations tell us…
– Solar system formed from a counterclockwise
rotating cloud of _____
• Sun formed. Everything else is leftovers.
• Asteroids, meteoroids, comets, and
planets formed from these leftovers.
• “Traditional” moons formed from the
leftovers of planets.
• Stay tuned to chapter 8 for more details.
Largest Bodies in Solar System – memorize
these in order: (good for your notecard)
1.
2.
3.
4.
5.
6.
7.
8.
9.
Sun
Jupiter
Saturn
Uranus
Neptune
Earth
Venus
Mars
Ganymede
J - biggest moon
10.
11.
12.
13.
14.
15.
16.
17.
Titan – S - atm. There’s a BIG jump
down to #18.
Mercury
Callisto – J - nothing impt.
Io – J - volcanoes
The Moon – big for parent
Europa – J - frozen water, ocean
Triton – N - geysers, backwards orbit
Biggest Pluto-like worlds
(Pluto is no longer the biggest
Pluto-like world!)
You will also need to memorize the “parent” object and the most important
things about each moon that’s unusual.
Features of the worlds
• The next few slides give a BRIEF
description of each planet + Pluto.
N
o
d
a
t
a
We have new
pictures from the
Messenger
spacecraft. I
haven’t included
those pictures yet.
Sorry.
Mercury
Small planet orbiting a big star. November 8, 2006
•
•
•
•
Mercury
Closest planet
Smallest planet (except Pluto)
Somewhat eccentric orbit
No atmosphere, no active volcanoes
– LOTS of Craters, past lava, “shrinkage” features
• 2nd hottest world (during day) -- 700K (425 ˚C, 800 ˚F)
• VERY cold at night – 100K (-180 ˚C, -280 ˚F)
– Caused by ______ rotation, caused by ________.
– 1 year has _____ days.
• Hard to see because near Sun. Visited twice so far
– Messenger launched in 2004.
– Took neat pictures earlier in 2008, 2009. Search APOD or Photojournal.
– Orbits in 2011.
• Made mostly of iron
– Most metal rich
– 2nd densest planet
Venus
Rotation Movie
Venus
• Same size as Earth (almost)
• Slow, backwards rotation. 1 year = 2 days
• THICK atmosphere. (92x Earth’s pressure = 1 km
underwater)
• VERY cloudy – can’t see ground with visible
light
• Hottest world -- 740K (470 ˚C, 880 ˚F) – “Traditional
view of Hell”
– STRONG Greenhouse Effect
– Day & night almost same temp.
• Volcanoes – active? All dormant?
• Continent-like features.
– Why “like”?
Earth and The Moon
Earth
• Biggest Terrestrial planet
• Fastest terrestrial planet rotation. 1 year =
365 days
• Densest planet
• Only atmosphere with oxygen (O2) [life
energy] and ozone (O3) [UV absorber]
• Liquid water on surface
• Most active surface
– volcanoes, erosion, tectonics
• Some greenhouse effect causes…
– Temp: 290 K (17 ˚C, 60 ˚F)
• Surprisingly large Moon
Mars
Rotation movie
Mars
•
•
•
•
Size: half Earth’s radius. 1/10th Earth’s mass.
Fast rotation. 1 “sol” = 24 h, 40m. 1 yr = 668 “sols” ( = 686 Earth days)
Thin atmosphere (CO2) – less than on top of Everest
Two tiny moons
– Probably captured asteroids. (Where is asteroid belt?)
•
•
•
•
•
Gets closest to Earth every 2 years … new spacecraft!
Dry now, but had lakes, rivers, maybe life!
Visited with dozens of robot spacecraft
Tall volcanoes, HUGE canyon
Polar ice caps (ice, dry ice)
Mars news
• Discovered in Jan 2009:
– Mars “belched” (released) significant amounts of
methane (CH4) in 2003.
– Solar UV light destroys methane
– The observed methane must be CURRENT
biological OR geological activity. Don’t know which.
• More studies are coming. Stay tuned!
• Show QuickTime methane movie in My Pics 
Mars
Jupiter
Show the Ganymede behind Jupiter movie!
Jupiter
• As big as planets get: 11x REarth & 300x MEarth
• Density = 1.3 g/cc (barely sinks in water)
• Gas outside, deep. Compressed interior.
– Gas squeezed: liquid first, then metallic, then solid
• Like all Jovian planets (& Sun): primarily H, He.
• 5 AU from Sun.
– Cold!
• Great Red Spot = hurricane 350+ yr old, 2x size of
Earth!
• 4 planet-sized moons. You know all about them…
• That’s enough…
Saturn
Show the Cassini ring movie!
Show Titan shadow movie
Saturn
• Also big: 10x REarth. Weigh the same on Earth!
• Counting rings, 30x REarth = Earth’s Moon’s orbit
– ALL Jovian planets have rings. Others hard to see.
• Rings = ice/rock pieces dust-sized to buildingsized. Average ring particle size: your desk
– Located inside Roche limit (strong tide stretching)
•
•
•
•
Density = 0.7 g/cc (FLOATS in water)
Similar composition & structure to Jupiter
10 AU away. That’s 2x Jupiter’s distance!
Only one big moon. Titan. Lots of small moons.
Uranus
Uranus
•
•
•
•
Pronounced YUR-uh-nus
Only 4x Earth’s radius, 15x Earth’s mass
20 AU away. Colder. 1 year = 84 Earth years.
Hydrogen forms molecules: water, ammonia,
methane (makes it look blue).
• Tilted on its side, probably from collision
– Unusual seasons from 98 degree tilt
• No big moons, but has rings (also “on side”)
• Only visited by one spacecraft (Voyager 2)
• Strange magnetic field: not centered on planet,
tilted 50 degrees! (Magnetic north near “LA”)
Neptune
Neptune
• Similar to Uranus in size, mass, composition, color
(blue), and strange magnetic field
• Like Uranus, not visible without telescope.
• Existence was PREDICTED based on deviations in
Uranus’ orbit. Observed soon afterwards.
• 1 Neptune year = 165 Earth years.
– Hasn’t had one full orbit since discovery (1846)
• Also only visited by Voyager 2
• Only one large moon: Triton
• Had (past tense) a Great Dark Spot. Disappeared
around 1994. (Was seen in 1989)
• All Jovian planets have storms.
Pluto &
Pluto-like
worlds
Pluto-like worlds
• Currently called “dwarf planets” or “plutoids”
– Plutoids look like nearby (Kuiper belt) comets
– There are 1000+ Kuiper Belt Objects similar to Pluto
– Pluto is no longer biggest one. Eris (2005). New, even
bigger, one coming in the news very soon.
• Pluto facts:
–
–
–
–
–
–
Size: 20% RadiusEarth and 0.2% of MEarth
Orbits in 250 years. Discovered in 1930
Distance 30-50 AU. Closer than Neptune 20 years.
Knew about 1 moon (Charon). Discovered 2 more!
Charon/Pluto BOTH synchronized rotation.
Never visited by spacecraft. New Horizons flies by in 2015.
Section 7.3 – spacecraft visits
• We have sent many spacecraft to the
planets, their moons, & our Moon.
• Any questions?
Summary
• Things that will be on the test:
– What Sun made of, its power source, solar wind
– What the similarities of the planets are (motions)
• Exceptions usually have explanations
– Differences between Terrestrial & Jovian planets
– What are asteroids, comets, meteoroids?
– 17 largest objects, “parent”, 1 neat fact for each
– Other major characteristics of the planets
• Not everything on each planet PowerPoint slide is “major”
– MAKE FLASHCARDS to study.
– Can bring a handwritten notecard, as always.