Download Chapter 16 - The Solar System

General Physical
Science
Chapter 16
The Solar System
The Solar System: An Overview
The
solar system is a complex system of
moving masses held together by
gravitational forces.
8 major planets
• Wanderers
3 dwarf planets
More than160 moons
Asteroids, comets meteoroids
Solar wind
• Charged particles, gases, interstellar dust
The Solar System: An Overview
Geocentric
Model
Everything rotates around the earth
• Pushed by the Catholic Church
• Very difficult to explain some observed motions
Heliocentric
Model
Copernicus
Revolves around the sun
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The Solar System: An Overview
Tycho
Brahe
Known for accurate measurement of the
positions of stars and planets
• Unaided eye!
Data analyzed by Kepler
Kepler then used this data to devise his Laws
of Planetary Motion.
Laws of Planetary Motion
First Law (Law of
Elliptical Motion)
All planets move in
elliptical paths around
the Sun with the Sun
as one focus of the
ellipse
Major axis
Semi--major axis
Semi
• For Earth, semi major
axis = 1 AU
Laws of Planetary Motion
Second
Law (Law of Equal Areas)
An imaginary line joining the planet and the
sun sweeps an equal area in an equal period
of time.
Perihelion
Aphelion
• Point that planet is closest to the sun (Jan. 4)
• Point that planet is farthest from the Sun (July 5)
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Laws of Planetary Motion
Laws of Planetary Motion
Third
Law (Harmonic Law)
The square of the sidereal period of a
planet is proportional to it’s semisemi-major
axis.
Sidereal
• Time for one revolution around the Sun
• 1 year for earth
T2 = kR3
• R = length of semisemi-major axis
• T = time
• When T in years, R in AU, then k = 1 year2 /
AU3
Example
Calculate
the period of a planet whose
orbit has a semisemi-major axis of 1.52 AU
T2 = kR3
R = 1.52 AU
k = 1 y2 / AU3
T2 = (1) (1.52)3 (y2 AU3 / AU3)
T2 = 3.51 y2
T = 1.87 y
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The Solar System and
Planetary Motion
Learning
Goals
Name some early astronomers and outline some
theories concerning the historical development of
astronomy as it relates to the solar system.
State and explain Kepler’s laws of planetary motion.
Questions:
1–4
Exercises: 1 – 11 odd
Major Planet Classifications and
Orbits
Galileo
Galilei
First to observe the Moon through a telescope
Observed 4 moons around Jupiter
• First to prove Earth not the only center of motion
in the universe.
universe.
• Showed that Venus had phases similar to the
Moon.
Major Planet Classifications and
Orbits
Issac
Newton
Incorporated work of Copernicus, Kepler,
Kepler, and
Galileo to formulate gravitational theory
Invented calculus
• Used to explain Kepler’s First Law
• Used Conservation of Angular Momentum to
explain Kepler’s 2nd Law
Mass
of the Solar System
99.87% of the mass is the Sun
• More than ½ of remaining mass is Jupiter
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Major Planet Classification
Inferior planets
Planets with their orbit inside that of Earth.
Mercury, Venus
Superior
planets
Planets with their orbit outside that of Earth.
Mars, Jupiter, Saturn, Uranus, Neptune, Pluto
Terrestrial
Jovian
(Earth-like) planets
(Earth-
Mercury, Venus, Earth, Mars
(Jupiter-like) planets
(Jupiter-
Jupiter, Saturn, Uranus, Neptune
Planetary Motion
Prograde
motion
Counter clockwise as viewed from the North
Pole
All planetary orbits
Most planetary rotation
Retrograde
motion
Clockwise as viewed from the North Pole
Venus, Uranus rotation
Relative Size of the Planets and
the Sun
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Major Planet Classifications and
Orbits
Sidereal
Period
Time for one orbit relative to a distant star
Conjunction
2 planets lined up with Sun
Inferior planets
• Same side – inferior conjunction
• Opposite Side – superior conjunction
Superior Planets
• Same side – conjunction
• Opposite sides – opposition
Conjunction and Opposition
The Solar System: An Overview
Learning
Goals
Describe the composition, structure, and motions of
the planets.
Questions:
5–7
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The Planet Earth
Unique
Large amounts of
surface water
• NOT only body with
water
Atmosphere contains
oxygen
Temperate climate
Living organisms
• As far as we know
Earth
Oblate spheroid
Slightly larger diameter at the equator than from pole
to pole (43 km)
due to Earth’s rotation
one part in 300 (1 inch in 25 ft)
Albedo 0.33
2 separate motions
rotation
revolution
Earth
Tilted
23.5O from orbital plane
tilt plus revolution leads to seasons
Focault
Pendulum
Proved rotation of the Earth
•
•
•
•
•
Released with no lateral motion
Direction of pendulum swing appears to change
Apparent change due to Earth’s rotation.
At the North pole rotation is 90O in 6 hours
Direction is constant relative to external reference
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Focault’s
Pendulum
Earth
Parallax
Apparent shift in
position of closer stars
against background of
farther stars
Simulate with finger
lined up with more
distant object
Use to determine
distance from stars
Earth
Parsec
Distance to a star when it exhibits a parallax
of 1 second (angular measurement 1/3600
degree)
Aberration
of starlight
Apparent change in direction of light from star
Snowflakes in snowstorm
Raindrops in moving car
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Facts and Figures
Earth
Learning
Goals
Identify some chemical and physical
properties of the Earth
Define and explain Earth’s two major motions.
Questions:
8 – 10
The Terrestrial Planets
Relatively small
Made up primarily of rocks and metals
High density (5 g/cm3)
Solid Surface
Magnetic fields
Relatively close to the Sun
No ring systems
Earth, Mars have moons
9
Mercury
Shortest revolution
(88 days)
Only visible at sunrise
or sunset
Surface similar to the
Moon
absence of significant
atmosphere
• Surface temperature
varies from - 180OC to
430OC
evidence that once
had thin atmosphere
Mercury – Facts and Figures
Venus
Closest to Earth
Third brightest object
in the sky
Very similar to Earth
Atmosphere 96% CO2
Surface temp 480OC
• Greenhouse Effect
Surface pressure 90
atm
10
Venus
Surrounded by clouds
Albedo 0.78
Mostly H2SO4 / H2O
Sulfur dust gives yellow color
Atmosphere rotational period 4 days (Retrograde)
Planetary rotation 243 days (retrograde)
Surface mapped by radar
May have been struck during formation
Many surface features
Evidence of former volcanic activity
Most features about 400 million years old
Venus – Facts and Figures
Mars
1.5 x as far from the
Sun as Earth
Tilted 24O
Rotation 24.5 hours
687 day synodic
period
2 small moons
Phobos (fear)
Deimois (panic)
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Mars
Moons
are tidetide-locked
Rotational period equals synodic period
Same as Earth’s Moon
= 3.9 g / cm3
Cratered
Density
‘Canals’
Polar
caps
Summer - H2O
Winter - H2O and CO2
Mars
Volcanic
activity
Olympus Mons
• 24 km high
Crater is 80 km and base is 600 km
• Largest known volcano in the Solar System
• Earth - Mauna Loa about 9 km
Martian
Exploration
From 1976 – present!
Mars
Valles Marineris
400 km long
6 km deep
Thought to be stress
fracture
Unmanned
exploration
Viking I (1976)
Pathfinder (1997)
• Sojourner
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Mars
Evidence of fluid flow
at one time!
Supported by findings
of Mars Global
Surveyor (2000)
The Terrestrial Planets
Origins
thought to be similar to Jovian
Planets
Predominant elements were H and He
Solar heat provided enough energy for these
gases to escape
Left behind the highhigh-density rocky core
Mars – Facts and Figures
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The Terrestrial Planets
Learning
Goals
List and compare the physical characteristics
of the terrestrial planets.
Questions: 11 – 13
The Jovian Planets
Gas
giants
No solid surface
Low density (average 1.2 g/cm3)
Inner rock core
• About the density of water
Lower
temperatures did not allow H and
He to escape
Significant Differences between
Terrestrial and Jovian Planets
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Jupiter
Largest Planet
d = 1.3 g/cm3
Liquid metallic
hydrogen with a rocky
core
Atmosphere
‘Bands’ on surface
H2, He, CH4, NH3
Mean temp –148OC
Great Red Spot
Perpetual storm
Jupiter
Shoemaker – Levy 9
Comet fragments
smashed into Jupiter’s
atmosphere
Visible from Earth
Dark spots approx.
size of the Earth!
Jupiter also has a ring
system
Not visible from Earth
Jupiter’s Rings
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Moons of Jupiter
16
or more observed
Difference is line between small moon and big
rock
Four
moons observed by Galileo in 1610
Io
Europa
Ganymede (largest moon in Solar System)
Callisto
Jupiter – Facts and Figures
Saturn
Most prominent feature
is the ring system
3 ring systems
A, B, and C
Rings formed by tidal
forces
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Saturn’s Rings
Many individual
ringlets
Color is computer
enhancement of
chemical composition.
Does have moons
Largest is Titan
Titan
Only satellite known
with a hazy
atmosphere
N2 (about 90%)
Ar (less than 10%)
Methane and other
hydrocarbons
Saturn – Facts and Figures
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Uranus
Discovered
Very
in 1781
Internal structure different than Jupiter and
Saturn
Less massive
Larger rocky core
thin ring system
Larger particles
Not much reflection
Uranus
Ring System
True Color Representation
Uranus – Facts and Figures
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Neptune
Twin of Uranus
Found in part by
mathematical
calculations based on
disturbances in orbit
of Uranus
Dark spot similar to
Great Red Spot on
Jupiter
Rings of Neptune
Were predicted by
blocking of starlight
Observations were
questionable.
Ring system
confirmed with
Voyager 2
Neptune – Facts and Figures
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The Jovian Planets
Learning
Goals:
List and compare the properties of the Jovian
planets.
Identify the major differences between the
terrestrial and Jovian planets
Questions:
14 – 17
The Dwarf Planets
Category
added in 2006 by International
Astronomical Union
Plutoids
Must orbit sun
Nearly round from selfself-gravity
Dominant body in it’s orbit
Ceres
Between Mars and
Jupiter
Discovered in 1801
Formerly classified as
an asteroid
Smallest of the dwarf
planets
20
Ceres – Facts and Figures
Pluto
Most distant from
the Sun
Discovered in 1930
by observers in AZ
Some similarities to
Uranus/Neptune
Not enough to
classify as ‘Jovian”
At times Pluto closer
than Neptune!
Charon
Satellite of Pluto
Largest satellite
relative to planet size
Discovered in 1978
½ size of Pluto
21
Orbital Plane
Pluto – Facts and Figures
Eris
Furthest from the Sun
Discovered in 2003
Slightly larger than
Pluto
Very elliptical orbit
22
Eris – Facts and Figures
…and beyond?
Kuiper
Most
Belt
From Neptune to Eris
Home for comets and cometary material
Exploration slated for 2015
distant object is Sedna
90 AU / 75 AU axes
Termination
shock
Edge of solar system
Solar wind meets interstellar material
The Dwarf Planets
Learning
Goals:
List and compare the properties of the Dwarf
planets..
planets
List the physical properties of Pluto
Questions:
18, 19
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Origin of the Solar System
Solar
Nebula
About 4.5 billion years ago
Began to condense under influence of it’s
own gravity
Condensation nucleus now part of the Sun
Conservation
of angular momentum
began to cause nebula to spin
Caused flattening
• Pizza dough
Origin of the Solar System
Kepler’s
Third Law stated that outer
material would rotate slower
Created ‘shear forces’
This
matter began to condense into the
planets.
planets.
Origin of the Solar System
Formed
Space
‘protoplanets’’
‘protoplanets
Protoearth probably 1000 x more massive
than the Earth today
Similar in composition to the Jovian planets
Heating of the terrestrial planets drove off
the gases
was ‘thicker’ with dust
Shielded planets initially from solar energy
Became clear from planetary accumulation
and solar wind transport.
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Origin of the Solar System
Learning
Goal:
Describe the theory for the origin of the solar
system that is most widely accepted by
astronomers.
Questions:
20 – 21
Other Planetary Systems
Difficult
to detect visually
Reflected light washed out by light from star
Observe
other effects
Gravitational
• ‘Wobble’
• Doppler effect
Over
200 other planets have been
detected indirectly!
Spectroscopically determined water on one
exoplanet
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Other Planetary Systems
Learning
Goal
Describe the methods used to discover
planets around other stars
Questions:
22 – 23
Terms; Matching, Multiple Choice,
and FillFill-in
in--the
the--Blank Questions; Visual
Connection and Applying your Knowledge
Key
General Physical
Science
Chapter 16
The Solar System
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