Transcript Quiz 4 Recap - Academic Computer Center

Quiz 4 Recap
17 November 2011
• Sunspots are cooler than their surroundings.
• Magnetic fields suppress rising hot gas in the
convective zone
• All planets orbit the Sun in the same direction
in approximately the same plane.
• How do we know the temperature of the Sun’s
photosphere is 5,800 K?
– Spectroscopy and Wien’s Law
– Stefan Boltzmann LawLuminosity/Radius/Temp Equation
• If you know R & L, can find T
• L = 4πR2σT4
Wien’s Law:
Inner Planets are Rocky
•Thin crust
•Generally thick, rocky (silicate) mantle
•Iron/Nickle core
•Chemical composition similar to Sun for elements
heavier than Hydrogen or Helium
•Low mass
•Dense
•Thin atmosphere
Outer or Jovian Planets
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All the Jovian planets are larger than the Terrestrial planets.
All have similar compositions and are similar to the Sun.
Solar composition is mostly Hydrogen, some Helium, etc.
All have low average densities,
All have rings and many satellites.
None have surfaces but only increasingly dense atmospheres
and rock and metal cores.
• High mass
• Thick atmosphere
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Outer Planets are More Massive
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The heat from the Sun
prevents ices from reforming
on the dust grains in the
region near the Sun.
Ices condensed only in the
outer parts of the Solar
nebula.
In the inner portion of the disk
only materials like iron and
silicates (rock) can condense
into solids. Slowly they form
clumps of material.
In the outer portion of the disk
much more material can
condense as solids including
ice. This extra material allows
clumps to grow larger and
faster.
•Both rock and ices (water, methane, ammonia) may form in the outer solar system.
•Since hydrogen is the most abundant element in the solar nebula, and it condenses
at lower temperatures, there is more planet building material in the outer solar system.
Outer Planets are More Massive
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The most abundant atom in
the universe is hydrogen
In our solar system,
molecules with hydrogen may
condense (change from gas
to liquid or solid [ice]) only in
the cool outer regions.
Therefore, there is more
planet building material in the
outer solar system.
•Both rock and ices (water, methane, ammonia) may form in the outer solar system.
•Since hydrogen is the most abundant element in the solar nebula, and it condenses
at lower temperatures, there is more planet building material in the outer solar system.
Outer or Jovian Planets
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All the Jovian planets are larger than the Terrestrial planets.
All have similar compositions and are similar to the Sun.
Solar composition is mostly Hydrogen, some Helium, etc.
All have low average densities,
All have rings and many satellites.
None have surfaces but only increasingly dense atmospheres
and rock and metal cores.
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Venus is the Hottest Inner Planet
• When the gases in an
atmosphere allow sunlight to
strike the surface the surface
heats up and gives off
infrared radiation.
• If the atmosphere however
prevents the infrared
radiation from radiating back
out to space the temperature
of the planet can increase,
this is the Greenhouse Effect.
• Carbon Dioxide CO2 behaves
this way and is an important
greenhouse gas. Venus’
atmosphere is 95% CO2.
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Why is Earth’s Atmosphere so
Different from Mars’ and Venus’?
• Water + CO2 makes carbonic acid = soda water
• Rain on Earth removes CO2 from the
atmosphere and locks it into the rocky ground
• Venus’ atmosphere is too hot for water to
condense out  no water rain to remove CO2
• Mars’ atmosphere is too thin and cold for water
rain
(may have fog)
– Mars does have CO2 snow at poles
– Mars currently has very little water in its atmosphere
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Why is Earth’s Atmosphere so
Different from Mars’ and Venus’?
• Role of Biology on Earth
• Plants use carbon-dioxide to make cellulose
• Sea creatures use carbon-dioxide runoff (from
rain) to make shells (calcium carbonate).
• Plants break down water and carbon dioxide by
photosynthesis, releasing oxygen into the
atmosphere
• Geological processes melt rock in the hot mantle
re-releasing carbon-dioxide into the atmosphere
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Surface Geological Activity on Earth is driven by Heat in its
Interior
Solar Granules
Top layer of convective zone
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Earth’s Interior
• The thin crust of Earth rides on
an elastic layer of rock called
the mantle.
• Below the mantle lies the liquid
outer core composed of iron
and nickel
• At the center is the solid inner
core also composed of iron
and nickel
• Motions within the mantle
cause the crust to be dragged
along. The crust is broken up
into “plates” that shift around
causing earthquakes,
volcanoes and forming
mountain ranges
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Jupiter’s (cool) atmosphere
has a mix of methane,
ammonia
and water.
Saturn’s (cooler)
atmosphere has a top
layer of ammonia ice
crystals, giving it a beige
visible color with some
bands.
Even colder Uranus and
Neptune have top layers
of mostly methane, giving
a blue, mostly featureless
appearance.
Saturn
Neptune
Uranus
When viewed in infrared light, which penetrates the
top layers of the atmosphere, the remaining outer
planets reveal wind-shear bands and storms
(bright, or hot spots) similar to those observed on
Jupiter in visible light images.
New Infrared Images of Saturn from
Cassini
Einstein’s Mass-Energy Relation
• In 1905 Albert Einstein
recognized that mass and
energy were related
through the formula:
E=mc2
(m =mass, E=energy, c=speed of light)
• What this means is that a
small amount of mass
could be converted into an
enormous amount of
energy.
• The means by which the
Sun generates this energy
is through nuclear fusion.
Albert Einstein (1879-1955)
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Nuclear Fusion
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The specific steps of nuclear
fusion follow a process
called the proton-proton
chain
Through this process 2
neutrinos, 2 positrons, 2 1H
and a 4He is created by the
fusion of 6 1H.
The mass of all the particles
created is less than the sum
of the masses of colliding
particles. This difference in
mass was converted into
energy through E=mc2.
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Hydrostatic Equilibrium
• Requires that the
pressure generated by the
fusion reactions in the
core of the Sun must be in
exact balance with the
weight of material falling
inwards due to the Sun’s
gravity.
• Without this balance the
Sun would either collapse
(gravity wins) or explode
(pressure wins).
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