Announcements

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Announcements
Students with last names starting from A to K go
to the Planetarium right now L to Z Thursday
(1100 a.m.)
1- 3 March Brooks Observatory tours
730-830 p.m. extra credit Bring back your
ticket with your name on the back
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March 2-18
Instructor Anatoly Miroshnichenko
E-mail astr1010_at_yahoo.com
The lecture notes are available
from http//ardbeg.astro.utoledo.edu/anatoly/ast
r1010/2004/materials.html
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Chapter 9

• The Giant Planets
• Jupiter, Saturn, Uranus, Neptune

• Internal Structure
• Atmospheres
• Magnetospheres
• Satellites and Rings

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Jovian Planets Basics

• Distance 5-30 AU
• Much farther from Sun than terrestrial planets
• Much colder (100-50 K)

• Mass 10-100 Earth masses
• Much more massive than terrestrial planets

• Jupiter Saturn are similar
• Size (about 10 Earth diameters)
• Composition mostly hydrogen and helium

• Uranus Neptune are similar
• Smaller than Jupiter Saturn
• Less hydrogen and helium

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Basic Parameters
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Appearance

• Jovian planets show banded appearance
• due to atmosphere
• we see only cloud tops

• Rotation quite fast (hours)
• Jupiter 10 hrs
• Saturn 11 hrs
• Uranus 17 hrs
• Neptune 16 hrs

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Clouds

• Clouds on Jupiter Saturn
  composed of ammonia ice (NH3)
• different colors due to differing cloud
  composition Saturns clouds deeper less visible

• Clouds on Uranus Neptune
• composed of methane (CH4)
• produces blue-green color

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Axial Tilt Seasons

• Jupiter
• only 3º axis tilt no real seasons
• Saturn
• 27º tilt normal seasonal variation
• Neptune
• 29º tilt similar to Saturn
• Uranus
• 98º tilt -on its side!collision?
• extreme seasons! each 21 yrs long

Seasons on Uranus
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Planet Interiors
Jupiter
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Jupiter Comet Encounter
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Comparing Jovian Planet Interiors
Density and size Jovian planets have very low
densities and similar radii The smallest stars
are even smaller in radius than Jupiter, but 80
times more massive Uranus and Neptune have
higher densities and a different chemical
composition (hydrogen compounds and rocks and
less pure H and He)
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Planet Density
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Jovian Planet Atmospheres
No solid surfaces Jupiter atmosphere Content
Almost entirely H and He trace amounts of
methane (CH4), ammonia (NH3), and H20. Jupiters
weather occurs in troposphere where clouds can be
formed of ammonia crystals and other compounds
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Jupiters Atmosphere
Wind is driven by the planets rotation. Jupiter
s rotation is so fast that the atmosphere breaks
up into many swirling bands.
The bands of rising air are called zones The
adjacent bands of falling air are called
belts Belts and Zones on Jupiter
Great Red Spot is the most dramatic weather
pattern in the Solar system (size of 2 Earths)
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The Great Red Spot
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Atmospheres of Other Planets
Different colors are due to trace gases or
colored compounds, produced by chemical reactions
Saturn has almost the same color as
Jupiter Uranus and Neptune are blue (due to
methane which absorbs red light and transmits
blue)
Saturn has belts and zones Neptune has bands and
a high-pressure storm Great Dark Spot Uranus has
slowly changing weather
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Magnetospheres
Magnetosphere consists of planets magnetic field
and particles trapped within them. Jupiters
magnetic field is 20,000 times stronger than
Earths. It deflects solar wind at 40 Jupiter
radii (3 million km).
The charged particles from Jupiters
magnetosphere bombard surfaces of Jupiters moons
which leads to release of their atmospheric gases
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Magnetospheres
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Jovian Planet Moons
There are more than 100 known moons orbiting
Jovian planets (J-52, S-30, U-21, N-11)
Three main groups of jovian moons Small moons -
less than 300 km in diameter Medium-size -
300-1500 km Large - more than 1500 km
Medium and large moons have circular orbits that
lie close to the equatorial planes of their
parent planets
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Jupiter Moons
Pre-visit expectations cold and geologically
dead Voyager missions the moons are active!
Four Galilean moons Io, Europa, Ganymede,
Callisto
Io has many volcanoes and no impact
craters Europa no craters, fractured surface,
icebergs Ganymede grooves on surface, magnetic
field Callisto a heavily cratered iceball
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Io
Eruptions erased all Ios impact craters.
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Reasons for Geological Activity
Io has an additional heating source tidal
heating Tidal heating is due to the Ios orbit
ellipticity. Io is continuously flexed by Jupiter.
Source of the orbit ellipticity orbital
resonances Periodical lining up of the three
closest satellites of Jupiter (Io 4 orbits,
Europa 2 orbits, Ganymede 1 orbit)
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Tidal Heating
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Orbital Resonance
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Europa

• Recently formed crust
• No craters
• tidal heating work

Visible icebergs suggest the presence of an ocean
below the surface. Latest news the ocean may be
made of acids
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Rings and Gaps
Two of Saturns rings can be seen from Earth In
fact, there are as high as 100,000 individual
rings and gaps Rings and gaps are caused by
grouping of particles at some orbital distances
which are being forced out at others.
Gaps can be created by gap moons located within
rings. They clear up gaps around their orbits.
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Rings of SaturnTelescopic view
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Rings of Saturn (Voyager image)
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Rings of Saturn (close up)
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Rings of Jupiter, Uranus and Neptune
These rings are much fainter than that of Saturn
and were discovered after 1977. The rings of
Uranus and Neptune were discovered during a
stellar occultation. Rings are similar to each
other. They lie in their planets equatorial
plane, particle orbits are almost circular, gaps
are due to gap moons. Saturns rings have larger
size, higher reflectivity, and greater number of
particles.
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Origin of the Rings
Ring particles may not last very long. They are
ground into dust in a few million years.
It should be a source of new ring particles. The
most likely one is collisions of small moons and
impacts between meteorites and small moons.
In the beginning, there were many more moons
around jovian planets. Gradual dismantling of the
moons created the ring systems.
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Summary of Jovian Planets

• Jovian planets larger, more massive than
  terrestrial
• Composition
• mostly hydrogen (H) and helium (He)
• dominated by hydrogen
• also large amounts of ices (water, ammonia,
  methane)
• Why So Large?
• basic reason is distance from sun
• cooler temps allowed ices (volatiles) to freeze

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Role of Volatiles

• Inner solar system is hot
• volatiles are gaseous not available for planet
  core formation
• planet cores
• only rock (no ice)
• smaller, less massive (1 earth mass)
• Outer solar system is cold
• volatiles are solid available for planet core
  formation
• planet cores
• both rock and ice
• bigger, more massive (10 earth masses)
• Massive cores have larger gravity can capture
  gas
• Jovian planets have massive atmospheres (lots of
  H and He)
• Terrestrial planets have minimal atmosphere
  (little H and He)

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Summary
Jovian planets are dynamic worlds with rapid
winds, huge storms, strong magnetic fields, and
interiors where common materials strangely
behave. Jovian moons are geologically active
because of their ice compositions. Ring systems
were formed from small moons. Study of jovian
planets brought new concepts of ice geology,
tidal heating, and orbital resonances.