Transcript Ch 13 PP
Chapter 13
The Solar System
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“Give
thanks to the Lord, for
he is good.
… who made
the great lights – the sun to
govern the day, the moon and
stars to govern the night; …”
Psalms 136:1, 7-9
Planets, moons and other
bodies
Our Solar System
Sun
8 planets ?
~100 moons
Thousands of asteroids, millions of
icy bodies, comets, …
Planets, moons and other bodies
Astronomical unit (AU)
Average Earth-Sun distance
1.5x108 km
1 km = 0.621 mile or 3280.8 feet
@ 93 million miles
(92,900,836.17
mi or 149,589,777 km)
Light –year (lt-yr) is used for longer distances
How
far light travels in one solar year
Speed of light = 186,282,3976 miles per second
5,880,000,000,000mi or 63,240 AUs !!!
Planet classification:
size
density
atmosphere
Two main divisions
Planets, moons and other bodies
1.
FourTerrestrial planets - mostly
rocky material, metallic nickel and
iron
Mercury
Venus
Earth
Mars
Planets, moons and other bodies
2. Four Giant Gas Planets - mostly hydrogen,
helium and methane
Jupiter
Saturn
Uranus
Neptune
Pluto
is now considered a dwarf planet
The order of the planets
Mercury
Innermost planet
2,439.7 km radius
Highly elliptical orbit
Average distance ~
0.4 AU (36 million
miles)
Orbital period (year) ~
88 days
Sun rise to sun rise
(“day”) ~ 176 days
Mercury
Visible shortly
after sunset or
before sunrise
No atmosphere;
No moon
40% smaller than Earth
Day hot enough to melt metal 427 C
Night cold as liquid nitrogen -173 C
Mariner 10 flew past Mercury in 1974
Magnetic field
Craters like our moon
Cliffs hundreds of kilometers high and long
Plains of smooth lava
Planets, moons and other bodies
12
Venus
Orbital distance ~ 0.7
AU (67 Million miles)
Morning and evening
“star”
Exhibits phases, like
the Moon
No moons
Rotational motion
opposite orbital
motion
Venus
Venusian “day” longer than Venusian
“year”
Visited by numerous probes
Mostly CO2 atmosphere, high temperature
and pressure
Surface mostly flat but varied
Venus
3rd
brightest in
sky
Called the sister
planet of earth
nearly same
size and
weight
Venus
Actually hotter than Mercury (900O F)
“Greenhouse” effect
Clouds of sulfur and CO2
462 C surface temperature
Besides “morning star” known as:
“witch star”
“dragon star”
“nearest you can get to hell”
(Russian Probe lasted less than an hour)
Earth’s Moon
1/6th gravity of earth
no atmosphere
one orbit takes 27
days
238,857 miles from
earth
never see dark side
12 Apollo astronauts
have walked on the
moon (1969-1972)
footsteps still there
Earth’s Moon
Lunar highlands
Light colored
mountainous
regions
craters
Breccias - rock
fragments
compacted from
meteorite impact
Earth’s Moon
Maria (“sea”)
Smooth dark areas formed from floods of
lava
Basalt - similar to rock formed from cooling
lava on earth
Formed about 3.1 – 3.8 billion years ago
Surface
3 meters grey dust containing microscopic
glass beads formed by bombardment of
meteorites
Moon Rocks
Glass
840 pounds brought
back
Stages in Formation of the Moon
Origin Stage
Moon formed from impact of Earth with very
large object, perhaps as large as Mars. The
moon formed from ejected material
produced by collision
Stages in Formation of the Moon
Molten Surface Stage
First 200 million years
Lunar surface melted due to rock impact
Fewer bombardments, moon surface
solidified
Craters: result of meteorite impact after
formation of crust
Stages in Formation of the Moon
Molten Interior Stage
3.8 billion years ago
Interior melted due to heat generated by
radioactivity
Cold and Quiet Stage
3.1 billion years ago
Last lava solidified
Little surface change since
Lunar Eclipse
Mars – the Red Planet
Mars
Orbital distance ~
1.5 AU (141 million mi)
One year is 687 days
One day is 24 hrs and
37 minutes
½ the size of earth
Numerous space
probes
2 moons
Deimos
Phobos
Mar’s Moons
Mars
Geologically active
regions:
Inactive volcanoes
Canyons
Terraced plateaus
Flat regions pitted
with craters
Mars
Thin atmosphere,
95% CO2--freezes at
the south pole
Strong evidence for
liquid water in past
Olympus Mons is 16
miles high
dust storms
Mars Spacecraft
Reconnaissance Orbiter (2004)
Spirit and Opportunity
Mars Exploration Rovers
Found that Mars
made of basalt
rock and
groundwater that is
dilute sulfuric acid
Confirmed
sufficient amounts
of water have been
present in the past
Spirit Rover
Spirit
ExoMars
2015
Earth
and
Moon
from
Mars
Jupiter
Jupiter
~ 5 AU from Sun
One orbit is 12 EY
Day is 10 hours
Most massive planet
483 million miles
318 times Earth’s
mass
200 pound man
would weigh 500
pounds
Jupiter
4th brightest object
in sky
Mostly H, He &
iron-silicate core
“Dynamic”
atmosphere
H2, He, ammonia,
methane, water,
Rings are present
Jupiter
Great Red Spot
permanent
“hurricane”
2-3 Earths
could fit inside
spot
Jupiter’s Moons
39 widely varying
satellites (moons)
Galilean moons:
Io (active
volcanos)
Europa
Ganymede
Callisto
1994 Shoemaker-Levy Comet
hits Jupiter
Saturn
Saturn
9.5 AU from Sun
886.2 million miles
10 hr day
29 1/2 years to orbit Sun
Second largest planet
10 times larger than earth
Many rings made of ice
and rocks
Mainly hydrogen and
helium
Surface similar to Jupiter’s
Very cold -285 F
Surface has dark and light bands
Rapid Rotation causes the equator to
bulge
Lowest Density = 0.7 that of water (float)
Saturn
30 satellites
Titan: Largest
(Mercury) only
moon in solar
system with
substantial
atmosphere
(nitrogen)
Uranus
Uranus
Uranus (~19 AU)
3rd largest planet
84 year orbit
16 hour day
27 moons
Rings present
1/400th sunlight earth
receives
Uranus’ Five Major Satellites
Neptune
Neptune: Blue Planet
(~30 AU) 3 billion km
165 years to orbit Sun
Great Dark Spot
Turbulent atmosphere
Very cold surface of
frozen hydrogen and
helium
13 moons
Triton largest moon
Pluto
Pluto:
Smaller than the
Moon
70% rock; 30%
water ice;
thin atmosphere
Unusual orbit
Tilted 17o from
ecliptic
Crosses
Neptune’s
Smaller bodies of the Solar System
Comets, asteroids,
meteorites
Leftover from solar
and planetary
formation
Mass of smaller
bodies may be 2/3
of total Solar
System mass
Bombard larger
objects
Comet structure
Small, solid
objects
“Dirty snowball”
model
Frozen water,
CO2, ammonia,
and methane
Dusty and rocky
bits
Comet structure
Comet head
Solid nucleus and coma of gas
Two types of tails
1. Ionized
gases
2. Dust
Tail points away from Sun
Asteroids
Located in belt
between Mars and
Jupiter
Sizes: up to 1,000 km
Asteroids
Varied composition
Inner belt: stony
Outer belt: dark with carbon
Others: iron and nickel
Formed from original solar nebula
Prevented from clumping by Jupiter
nearby
Meteors and meteorites
Meteoroids
Remnants
of
comets and
asteroids
Meteors and meteorites
Meteor
Meteoroid encountering Earth’s
atmosphere
Meteor showers: Earth passing through
comet’s tail
Meteorite
Meteoroid surviving to strike Earth’s
surface
Origin of the Solar System
Protoplanet nebular
model
Stage A
Formation of heavy
elements in many
earlier stars and
supernovas
Concentration in one
region of space as
dust, gas and
chemical compounds
Origin of the Solar System
Stage B
Formation of large,
rotating nebula
Gravitational
contraction, spin
rate increases
Origin of the Solar System
Most mass concentrates in central protostar
Remaining material forms accretion disk
Material in accretion disk begins clumping
Origin of the Solar System
Stage C
Solar ignition flare-up
may have blown away
hydrogen and helium
atmospheres of inner
planets
Protosun becomes a
star
Origin of the Solar System
Protoplanets heated, separating heavy and
light minerals
Larger bodies cooled slower, with heavy
materials settling over longer times into
central cores