Transcript Chapter 29 The Solar System

Our Solar System
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BIG Idea:
• Using the laws of
motion and gravitation,
astronomers can
understand the orbits
and the properties of
the planets and other
objects in the solar
system.
I. Models of the Solar System
A. Geocentric: the Sun, stars, and planets
revolved around the Earth.
– Aristotle promoted
this Earth-centered model
B. Heliocentric – the sun is the center of
the universe
- Copernicus proposed this model
Kepler’s Laws
• Explained planetary
motion mathematically
1. Law of Ellipses: explains a planet’s path
around the Sun
►Ellipse: an oval whose shape is
determined by two points (foci)
►The Sun is at one focus of the orbit of
a planet
• Because the planets’ orbits are
elliptical, they are not always the same
distances from the sun…
– Do you remember the word to describe
the point in our orbit when we are closest
to the Sun?
– Farthest away?
• There are TWO types of
planets in our solar system…
• How were you taught to
remember them?
Planet Acronyms
• My Very Excellent Mother Just
Served Us Nachos
• My Very Excellent Mother Just
Served Us Noodles
• My Very Educated Mother Just
Served Us Nachos
II. The Inner Planets
(4 planets closest to the Sun)
• Terrestrial Planets: Earth-like
(rocky)
A. Mercury
• Closest to the Sun
• Shortest orbit of 88
days
•Heavily cratered
•Huge temperature
range 427ºC in
day, -173ºC at
night
Mariner 10 – visited the planet in 1974
and 1979
B. Venus
• Earth’s twin (size,
mass, density)
• Rotation direction is
opposite that of other
planets
• Pressure is 90x Earth’s
Hot surface
(464ºC)
Dense
atmosphere
(mostly CO2)
Magellan Probe
C. Earth
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Third planet from Sun
Orbital period of 365.24 days
Completes one full rotation in 23 hours 56 minutes
Fifth largest planet
Located between the Sun
and the asteroid belt
• One natural satellite, the
moon
Life on Earth is possible because…
• …of the Earth’s distance from the Sun
Temperature is warm enough for water to
exist as a liquid
Water occurs on Earth as a solid (ice), a
liquid, or a gas (water vapor)
The only known planet with the proper
combination of water, temperature, and
oxygen to support plant and animal life
Earth’s Atmosphere
What causes the seasons on Earth?
• Earth’s revolution around the Sun,
TILTED ON ITS AXIS !
D. Mars
• Axis is tilted like Earth’s
• Very thin atmosphere (mostly
CO2)
• Olympus Mons – shield volcano
 Largest known volcano in
our solar system
 3X higher than Mt. Everest
Viking 1 – found evidence
of water erosion
III. The Outer Planets
• Jovian Planets: Jupiter-like gas giants
A. Jupiter
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Largest planet
Fastest rotation - every 10 hours
Orbital period is 12 years
More than 60 moons
Mostly hydrogen and helium
Great Red Spot – giant
rotating storm
(over 300 years long)
Galileo
B. Saturn
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Average temp: -176ºC
Least dense planet
Orbital period is 29.5 years
Complex system of rings
Cassini Spacecraft
C. Uranus
• Rotates horizontally
• The ‘tipped’ planet
• Orbital period is 84
years
• Greenish color
• Methane atmosphere
Voyager 2
D. Neptune
• Orbital period is 164 years
• 8 moons and possibly 4 rings
• Upper atmosphere composed of white
clouds of frozen methane (appear as bands
moving between equator and poles)
• Great Dark Spot – huge storm
• Solar system’s strongest winds – exceeding
1,000 km/hr
IV. Other Solar System Objects
A. Dwarf Planets
• An object that, due to its own
gravity, is spherical in shape, orbits
the Sun, is not a satellite, and has not
cleared the area of its orbit of
smaller debris.
1. Pluto
(now ‘asteroid #134340’)
• Late to be discovered (1930)
• Mostly frozen methane, rock,
and ice
• Demoted from planet
status to “dwarf planet”
in August 2006
Not always the furthest
planet from the sun
2. Ceres: largest body in
the Asteroid Belt
3. Eris:
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largest known dwarf
planet
27% more massive than
Pluto
B. Small Solar System Bodies
1. Asteroids
• thousands orbiting
the Sun between
Mars and Jupiter
• rocky bodies
• vary in diameter
• pitted, irregular surfaces
Asteroid Belt
• between Mars and Jupiter
• remains of unformed planets
(planetesimals)
 meteoroid: small bits of rocks and metal left
by a comet or asteroid collision
 meteor: bright streak of light produced by
meteoroids burning up as they enter our
atmosphere
 meteorite: meteoroid (or part of one) that is
left after it hits the Earth
• Meteor Shower
“shooting stars”
• Meteorite: meteoroid that makes it
to Earth
• When large meteorites strike Earth,
they produce impact craters:
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2. Comets
• small, icy bodies of rock, dust,
methane and ammonia
• orbit the Sun in long ellipses
1. Nucleus: small solid core, which is
made up of rocks, metals, and ice
2. Tail: gas and dust
In relation to the Sun, what do you
notice about the tails of the
comets?
• The tails always point AWAY from
the Sun!
• Their tails of gas and dust are
pushed away by radiation from the
Sun.