Section 11: Giant Planets - Jupiter, Saturn, Uranus, Neptune

Giant Planets/ Jovian Planets

• Make up 0.13% of the solar systems mass

• All have large orbits due to their larger gravities 

• Lower densities 

• Jovian Planet Core: All have a rock or ice core 

• Rotation: All rotate quickly on their y axis

• Differential rotation: Found in Jovian planets with atmospheric bands 

• Magnetism: very strong and found in all jovian planets caused by…

• HEating

• Lower densities 

• Different densities: Caused by various compression of the gasses by gravity 

  • Bigger planet = greater gravity = more compression

  • COmpression effects: HYdrogen is in the form of metallic liquid 

• Rotation in jovian planets

• Due to conservation of angular momentum: L=mrv

  • Larger the radius larger the velocity since its proportional

  • More gas being collapsed inwards making it speed up 

• Surface rotates even quicker since they are so large 

• Axial Tilts: Found in all jovian planets 

  • They all have seasons and changing day lengths 

Differential rotation:

• Found in Jovian planets with atmospheric bands 

  • Their atmosphere is sectioned and rotate at different rates, and also different at different depths 

    • Most noticeable in the sun: with differences up to 10 days

  • FUnction of Latitude: Depends on the distance from the equator 

Magnetism

• very strong and found in all jovian planets caused by…

1. Convection

2. Rotation 

3. Conduction → usually their core

Magnetism causes aurorae

• Create aurorae →when charged particles from the sun, known as the solar wind, collide with gases in Earth's upper atmosphere

• HEating in Jovian Planets: 

• Heating is suggested to be caused by the compressing gas to a high pressure 

• Emits more heat themselves than they receive from the sun 

• Based on Blackbody Law higher temps = more light energy is being emitted 

  • They are therefore hotter than the equilibrium and are are slowly cooling

Convections

• Caused by the strong heating at the equator and hot air rises and then it cools at the poles and the cold air falls back down to the equator  

• Convection cells

1. Hadley cells: The ones next to the equator 

• East to west winds 

2. Ferrel Cells: Between the hadley and polar cells

• West to east winds

3. Polar cells: the ones at the poles

Coriolis Forces

• Angular momentum wont allow air to flow straight north or south rather it bends in the opposite direction the planet is rotating ALways to the right in the northern hemisphere 

  • Going to the poles that rotate more slowly so it will be ahead

  • Going to the equator its not caught up so it will be behind 

• Always to the left in the southern hemisphere

 Hurricanes, typhoons and Cyclones

1. Hurricanes: Northern east hemisphere - Counterclockwise to the right 

2. Typhoon: Northern west hemisphere - Counterclockwise to the right 

3. Cyclone: In the southern hemisphere - clockwise to the left

Fast Rotation

• Various conventions and rotation speeds lead to the banding and cells  

Jupiter

• Visible with a Telescope

  • Jupiter

  • It’s four galilean moons 

  • Great red spot 

    • A perpetual storm/hurricane

    • A lot of rotation keeps it going 

    • Deep atmosphere with minimal friction (no land) forces to stop it  

  • Banded atmosphere 

Jupiter Composition

• Hydrogen and helium

  • Internal Volume: Liquid hydrogen 

• Core: Metallic hydrogen/ liquid hydrogen → conducts 

  • Jupiter's magnetic field is so strong it takes over the sun's field and helps prevent solar winds in that region 

Jupiter heating

• Heat from initial formation → Primordial Heat

• HEat from compressed gas

Jupiter Rotation

• Axial Tilt: Very small, minimal seasons (3^o)

• Differential Rotation: 

  • Poles rotate a lot slower than the equator 

• Cells Created by Convections: Jupiter banding 

• Jupiter Banding: 

• Light zones and dark belts rotate at different rates and in different directions 

• Different colours: Caused by cooling and heating of different chemicals creating new compounds causing colour changes 

  • White bands: Light zones are areas of strong upwelling, higher altitudes 

  • Dark bands: Dark belts are areas of strong downflow, with lower altitudes  

• Convection moves gas up and down, but due to the coriolis effect the rotation makes those flows curve sideways

• ANgular momentum is channeled to the equator → making it spin faster

• Multiple convection cells

Saturn

• Rings and its gaps

  • Cassini Division: the most notable gap in Saturn's rings

• Atmospheric Bands

  • Haze on top of atmosphere making it seem smoother

Saturn Atmosphere

• strong  internal  heating  and  strong  rotation causing a dynamic atmosphere and banding

• Bands: seen in infrared wavelengths

Saturn Composition

• Hydrogen and helium

  • Internal Volume: Liquid hydrogen 

• HIgh altitude white haze created by crystals 

• Core: Metallic hydrogen/ liquid hydrogen 

Saturn Heating

• Primordial heat

• Helium rain → gravitational potential energy is released in the form of heat

Saturn Rotation

• Axial Tilt: Tilted by 26.7^o

• Strong rotation 

Uranus

• Uranus can be seen with the naked eye 

  • Similar to a star in the sky 

  • Discovered by William Herschel 

• Nearly featureless

Uranus Atmosphere

• Mainly composed of methane (CH₄) → reflect blue

• Very thick high altitude haze with only some visible clouds

  • Less altitude heating leaving to significantly less banding

Neptune Compositon

• Denser and heavier icy/ rocky materials 

• Small layer of hydrogen on top

• Core: Dissolved Ammonia and water as well

Uranus heating…?

TRICK QUESTION NYAH NYAH

• Lack of heating → Its primordial heat is gone 

Uranus Rotation

• Axial Tilit: Heavily tilted by 97.8^o

  • Experiences extreme seasons

• Slower rotation than jupiter, neptune and saturn 

Neptune discovery

• Determined due to Uranus orbit being unexplained by a simple Kepler Ellipse suggesting a separate planets’ gravitational force was effecting it 

Neptune

• Blue hue → SImilar to uranus just slightly lighter 

• Atmospheric bands and clouds 

• Great Dark spot → no longer there

Neptune Atmosphere

• Methane rich → also gives a blue 

• More active than uranus leading to bands and spots

  • Has a source of internal heating

Neptune Composition

• Denser and heavier icy/ rocky materials 

• Small layer of hydrogen on top

• Core: Dissolved Ammonia and water as well

Neptune Heating

• Primordial heat still present 

• Methane possible insulates the planet 

Neptune Rotation

• Axial Tilt: Tilted by 28.3^o

• Faster rotation than uranus but still slower than jupiter and saturn

Different Spacecrafts

1. Pioneer programs

2. Voyager 1 and 2

3. Galileo 

• Dropped a probe into jupiter 

• Helped analyze structure and atmosphere composition 

4. Cassini 

• Dropped a probe onto titan (Saturn's largest moon)

• Takes pictures 

Spacecraft Movement uses 2 things

• Gravitational Slingshots: Used to adjust the speed and the direction of spacecrafts to save fuel 

  • Launch dates and times are calculated to use these

  • Natural Slingshots: Flying objects that are accidentally taken in 

    • Comets coming close and they get ripped apart 

• Conservation of Angular Momentum: Planets orbit affected a negligible amount, while spacecraft's trajectory get greatly altered