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Chapter 15: The Solar System
I.
The Solar System
A.
Ideas of solar system
1. Earth-centered model: Greeks
2.
3.
a.
The planets, sun, stars, and moon
were in separate spheres
b.
All rotating around Earth
Sun-centered model
a.
1543, Copernicus had a different
view
b.
The moon revolved around Earth
c.
Earth and other planets revolve
around the sun
d.
Galileo Galilei observed Venus went
through phases like the moon,
supporting this model
Modern view
a.
Solar system: system of eight
planets, including Earth and other
objects that revolve around the sun
1)
sun contains 99.86% of the mass
of the system
b.
Sun is the center with all other
objects revolving around it
B. How the solar system formed
1.
Formed from a nebula of gas, ice, and
dust
2.
A cloud of material in the nebula
slowly rotated
3.
A nearby star may have exploded
sending out shock waves, causing the
cloud to contract
4.
Gravity pulled particles inward making
it more dense, rotated faster, heated
up, and flattened to form a disk
5.
During contraction the temperature in
one cluster reached 10 million oC,
starting nuclear fusion - sun began
6.
Planet formation from leftover
material
a.
Inner planet - small, rocky, iron
core
b.
Outer planets - large, lightweight
except Pluto
C. Planet motion
1.
Copernicus theorized the planets had
circular orbits around the sun
2.
Johannes Kepler discovered the orbits
were elliptical (oval)
a.
Calculations also showed the sun
was offset of center
b.
Planets travel at different speeds
1)
larger planets take longer to
revolve around the sun
II. The Inner Planets
A.
Mercury: closest planet to the sun,
smallest
1.
Mariner 10 photographed 45%, other is
unknown
2.
Weak magnetic field suggests iron core
3.
Has many craters and high cliffs
a.
4.
No true atmosphere
a.
B.
Caused by contraction of crust
Temperature range from 425oC to
-170oC
Venus: second from sun, similar to Earth
in size and shape (Earth’s twin)
1.
Magellan probe mapped 98% of surface,
noticed huge volcano
2.
Extremely dense atmosphere of clouds
3.
C.
D.
Carbon dioxide gas traps solar energy
a.
Causes an intense greenhouse effect
b.
Results in surface temperatures
between 450oC and 475oC
Earth: third planet from sun
1.
Average distance between Earth and the
sun is 150 million km
2.
Water exists on surface as solid,
liquid, and gas
3.
More than 70% of surface covered with
water
4.
Atmosphere protects surface from most
meteors and sun’s radiation
5.
Is tilted on its axis, which causes
seasons
Mars: fourth planet from sun
1.
Called red planet because iron oxide
in rocks makes them reddish-yellow
2.
Polar ice caps made mostly of frozen
carbon dioxide and water
3.
Has largest volcano in the solar
system - Olympus Mons
4.
Soil shows no evidence of life - found
by Viking probe
5.
Has gullies and deposits of soil and
rocks, which may indicate the presence
of liquid groundwater
a.
H2O occurs as frost beneath thin
layer of soil
b.
Spirit & Opportunity rovers
analyzed rock for life
6.
Thin atmosphere of mostly carbon
dioxide
7.
Strong winds caused by differences in
temperature between day and night
8.
Is tilted on its axis, which causes
seasons
9.
Two small moons: Phobos and Deimos
III. The Outer Planets
A.
Jupiter: fifth planet from the Sun,
largest planet in the solar system
1.
Faint dust rings
2.
Atmosphere - primarily hydrogen and
helium
a.
Below atmosphere, liquid hydrogen
and helium are suspected
b.
Solid rocky core may exist below
liquid layer
c.
3.
The Great Red Spot is the most
spectacular of Jupiter’s many
constant high-pressure gas storms
Has at least 63 (61) moons - four are
relatively large and have atmospheres
a.
Io - is very volcanically active,
the closest large moon to Jupiter
b.
Europa - composed mostly of rock,
may have an ocean of water under a
thick layer of ice
c.
Ganymede - largest moon in the
solar system (larger than Mercury)
d.
Callisto - cratered rock and ice
crust may surround a salty ocean
and rock core
B. Saturn: sixth planet from the Sun, second
largest in the solar system, lowest
density
1.
Thick outer atmosphere of hydrogen,
helium, ammonia, methane, and water
vapor
2.
Might have a small, rocky core
3.
Each large ring is composed of
thousands of ringlets of ice and rock
particles
a.
4.
Particles vary in size from specks
of dust to tens of meters
Has at least 60 (31) moons
a.
Largest moon, Titan, is larger than
Mercury
b.
Thick clouds on Titan prevent
scientist from seeing surface
C. Uranus: seventh planet from the Sun, large
and gaseous
1.
Has 11 thin, dark rings at the equator
2.
Atmosphere of hydrogen, helium, and
methane
3.
Methane makes the planet bluish-green
in color
a.
4.
Methane absorbs red and yellow
light, reflects blue and green
Axis of rotation nearly parallel to
plane of orbit (rotation is tilted on
its side)
D. Neptune: the eighth planet, large and
gaseous
1.
Bluish-green colored atmosphere
similar to that of Uranus
2.
Storms on Neptune reveal an active and
rapidly changing atmosphere
3.
Has at least 13 (11) moons, of which
pinkish Triton is largest
E. Pluto: the ninth satellite from the Sun,
sub-planet in the solar system
1.
During part of its 248 yr orbit Pluto
is closer to the Sun than Neptune
2.
Has a thin atmosphere and a solid,
rocky surface
3.
Discovered in 1978, moon Charon is
half the sub-planet’s size
a.
4.
Close size and orbit makes some
scientists believe it to be a
double planet
Hubble Space Telescope reveals group
of icy comets named Kuiper Belt beyond
Neptune’s orbit
a.
Some scientist believe Pluto and
Charon are members of the Kuiper
Belt not a planet and moon
IV. Other objects in the Solar System
A. Comet: dust and rock particles combined
with frozen water, methane, and ammonia
1.
Halley’s comet orbits the sun every 76
years
2.
Oort Cloud: a cloud of comets
surrounding the solar system beyond
Pluto
3.
Comet Hale-Bopp was discovered in 1995
by two amateur astronomers
4.
Comet structure - is similar to a
large dirty snowball of frozen rock
and ice
a.
Ice and dust vaporize as comets
near the sun
b.
Coma: a cloud of vaporized material
that forms around the comet nucleus
c.
Solar winds push on gas and dust in
the coma, causing the particles to
form a tail that always points away
from the sun
d.
Eventually, most of the ice in the
nucleus vaporizes leaving particles
throughout its orbit
B. Meteoroids, meteors, and meteorites
1.
Meteoroids: name given to small pieces
of comet when they move through space
2.
Meteor: small meteoroid that burns up
in Earth’s atmosphere
a.
3.
Meteor showers occur when Earth
passes through a group of
meteoroids
Meteorite: meteoroid that strikes
Earth
C. Asteroid: rock similar to that which
formed the planets
1.
Asteroid belt: area between Mars and
Jupiter where most asteroids lie
2.
Jupiter’s gravity may have kept these
asteroids from forming a planet
3.
Some planets’ moon may be asteroids
pulled from the asteroid belt
4.
Asteroid sizes range from very tiny to
940 km in diameter