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Ch. 3 The Solar
System
Section 1
The Solar System
Inertia and Gravity
•Inertia:
•The tendency of an object to
continue on a straight line or a
stationary object to remain in place.
•The more mass = more inertia.
•Inertia & Gravity combine to
keep the planets in orbit around
the sun.
Observing the Night Sky
•Geocentric (Earth Centered):
•The Earth at the center, the sun
and all other planets orbiting
around the Earth.
•WRONG!!
•Gravity:
•The attractive force between two
objects.
•The strength depends on the
mass of the object and the
distance between the objects.
Our Solar System
•Solar System•Is made up of the eight planets and
many other objects held in orbit by
the sun.
•Mercury, Venus, Earth, Mars, Jupiter,
Saturn, Uranus, Neptune.
Observing the Night Sky
•Heliocentric (Sun Centered):
•The sun at the center of the solar system.
All the planets are in orbit around the
sun.
•Proposed by Copernicus and proven by
Galileo’s observations.
•Jupiter had moons.
•Venus went through phases like our moon.
•CORRECT!!
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Begins of a Solar System
•Protoplanetary disk•is a rotating disk of dense gas and dust
surrounding a young newly formed star
•Astronomical Unit (AU)
• The distance from the Earth to the sun.
• About 150,000,000 km
• Used as a measurement scale to simplify the
distance between planets.
•Planetesimals•Planets form out of dust grains that
collide and stick to form larger and
larger bodies
•Accretion•Accumulation of material to
form larger and larger objects.
•The planets!!
Formation of The
Solar System
•Phase I (started 5 billion years ago)
•Gas Cloud starts to collapse in on itself
due to its own gravitational pull.
•As it collapses, it rotates faster and
becomes flatter.
•Phase II
•The sun forms in the central part of the
gas cloud
•nuclear fusion start in its core.
•Phase III
•Dust grains and ice crystals start to
condense to form planetesimals from
collisions
•(objects the size of the Moon)
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•Phase IV
•Planets grow by successive
bombardment of planetesimals.
•Outer massive planets grab the
remains of the gas from the cloud.
•Planets formed
•Still some debris around (asteroids and
comets) that occasionally hit the planets.
Ch. 2 The Solar
System
Section 2
Inner Planets
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Early in the Life of Planets
•Planetesimals swept up debris
•Accretion + Impacts = HEAT
•Eventually begin to melt materials
•Iron, silica melt at different temperatures
•Iron sank – density layering
•Examined close-up, They
are very different…
• Mercury and Earth’s Moon are
airless and barren
• Mars has a very thin atmosphere
• Earth has oxygen, water, and life!
• Venus has a thick atmosphere and
very hot and toxic!
Similarities and Differences of the
Terrestrial Worlds
From a distance, they appear very similar…
• Small, dense and rocky!
• Close to the sun
• No or few moons
Internal Structure of the
Terrestrial Planets
They all have:
•Core –
• High density metal
•Mantle –
• Medium density rocky materials, such as silica
(SiO2), hot, semi-solid
•Crust –
• lowest density rocks, such as granite and basalt.
•Mercury
Average: 57 million km (.387 AU)
•Venus
Average: 108 million km (.722 AU)
•Mars
Average: 228 million km (1.52 AU)
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The Inner Planets:
•Mercury:
•Closest to the sun.
•No atmosphere.
•About the size of our Moon.
•Surface has many craters and high cliffs.
•Temperature range:
•Mercury:
• The surface of Mercury has many craters and
looks much like Earth's Moon.
• It also has cliffs as high as 3 km on its surface.
• These cliffs might have formed at a time when
Mercury shrank in diameter.
•4250 C day to -1700 C at night
•No moons
The Inner Planets:
•Venus:
•About the same size as Earth.
•Thick atmosphere (mostly CO2)
•Yellowish in color because of
sulfuric acid rain.
•Temperature range:
•450 – 475 0 C
The greenhouse Effect
1. Sunlight streams through
the glass into the
greenhouse.
3. The glass stops
the heat from
escaping to the
outside.
2. Sunlight is
absorbed by
objects inside the
greenhouse. The
objects radiate the
energy as heat.
The gases in the atmosphere act like a layer of glass.
The gases allow solar energy to pass through, but some of
the gases trap thermal energy.
•No moons
Radiation in the Atmosphere
Radiation, Convection, Conduction
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The Inner Planets:
•Earth:
•Our home!!
•Atmosphere protects life.
•Surface temperatures allow water
to exist as solid, liquid, and gas.
• 13 to 17 degrees Celsius
•Has one large moon.
The Inner Planets:
•Mars:
•Mars:
•Evidence of surface water-
•4th
planet from the sun.
•Surface appears reddish because of iron
oxides in the soil. (rust)
•About half the size of Earth.
•Surface temperatures range
•Night -1250 to 350 C day.
•Very thin atmosphere (CO2)
•Ice caps of frozen CO2 at the poles.
•Two small moons.
•Surface erosion and water ice in crater.
•Largest volcano in the solar system
•Olympus Mons
•Mars has seasons just like here on
Earth.
•Massive dust storms, freezing and thawing of
CO2 ice.
•Moons:
•Phobos is about 25 km in length
•Deimos is about 13 km in length.
Surface Erosion
Water Ice
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Ch. 2 The Solar
System
Section 3
Outer Planets
•Jupiter:
•Jupiter
Average: 779 million km (5.20 AU)
•Saturn
Average: 1.43 billion km (9.58 AU)
•Uranus
Average: 2.88 billion km (19.2 AU)
•Neptune
Average: 4.50 billion km (30.1 AU)
The Outer Planets
• Largest planet made of gases.
• 1,300 Earths could fit inside Jupiter!
• Atmosphere is mostly hydrogen and helium.
• 5 AU from the Sun.
• Massive continuous storms swirl.
• The Great Red Spot!
• Four large moons:
• Io has active volcanoes!
• 59 smaller moons
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•Saturn:
The Outer Planets
•Second largest
•About 764 Earths could fit inside Saturn.
•Thick atmosphere of hydrogen and
helium gas.
•Turns into liquid closer to the center!
•Complex system of rings.
•Thousands of rings.
•Composed of ice and rock particles.
•47 moons
•Titan is the largest (bigger than Mercury!)
•Uranus:
The Outer Planets
• Atmosphere is hydrogen, helium, and
methane.
• Methane gives the planet bluish color.
• 63 Earths could fit inside of Uranus.
• Temperature is -2180 C
• Average distance from sun is ~19 AU
• Axis of rotation is nearly parallel to the
plane of orbit.
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The Outer Planets
•Neptune:
•Very similar to Uranus!
•Atmosphere is hydrogen, helium, and
methane.
•Methane gives the planet bluish color.
•Temperature is -2180 C
•Average distance from sun is ~30 AU
•Stormy spots similar to Jupiter’s Red
Spot.
•57 Earths could fit
inside of Neptune!
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Ch. 3 The Solar
System
Section 4
Comets, Asteroids, and Meteors
Comets, Asteroids, and Meteors
•Comets:
•Chunks of ice and dust.
•Dirty snowballs!
•Very long and elliptical orbits.
•Three features to a comet:
•Nucleus
•Coma
•Tail
Features of a Comet!
•Nucleus
• rock & ices (mostly H2O and CO2 [dry ice], some
methane CH4 & ammonia NH3)
•Coma
• is gaseous. As comet approaches Sun ices
sublime, change from solid to gas, dust grains
loosen and move away
•Nucleus
•Coma
•Ion tail
•Dust tail
•Tails —
• solar wind (steady stream of solar particles)
pushes gas away; dust continues to orbit Sun
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Halley’s comet was at perihelion in 1986
It will return in 2061.
• Most comets originate in the Kuiper belt at
the extreme edges of the solar system.
•Asteroids:
• Small rock bodies mostly silica and iron.
•Asteroid belt:
• Location where most asteroids orbit the sun.
• Between Jupiter and Mars.
•Meteoroids:
•A chunk of rock (silica and iron) in
space.
View of 3 asteroids from spacecraft
•Meteor:
•When a meteoroid enters Earth’s
atmosphere friction makes it burn up
and produces a streak of light.
•Meteorite:
•Is a meteoroid that reaches the surface
of Earth.
50 km
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Impact Crater in Arizona
The projectile that exploded on impact and produced Meteor
Crater was equivalent to the energy of 1000 Hiroshima bombs.
20 megatons!
The END
Telescopes
Telescopes help astronomers
in two ways:
• They collect far more light than an
unaided eye can.
• They magnify images so you can see
more detail and to visually separate
distant objects from one another.
•Refracting telescopes
•use lenses both to focus light and to
magnify an image for viewers.
•These are the original type of telescope.
•Reflecting telescopes
•use one mirror to focus light and a second
mirror to reflect the light to the eyepiece.
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Radio Telescopes
•Radio telescopes
•gather information from radio waves.
•Clouds don’t disrupt the collection of radio
wave data, but electrical storms do.
•These telescopes can collect data during
the day or night.
•They are large because radio waves have
longer wavelengths than visible light.
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