The Outer Planets The Outer Planets

The Outer Planets The Outer Planets

Section 27.2

Section 27.2

Jovian Planets Jovian Planets

 The Inner and Outer The Inner and Outer planets are separated planets are separated

by the

by the asteroid belt asteroid belt

 Jupiter’s moons were Jupiter’s moons were discovered by Galileo.

discovered by Galileo.

 Uranus and Neptune Uranus and Neptune weren’t discovered weren’t discovered

until the invention of until the invention of

the telescope

the telescope

Great Balls of Gas Great Balls of Gas

 The jovian planets are truly “other-worldly”. The jovian planets are truly “other-worldly”.

 Many times Many times larger larger and more massive than and more massive than Earth, but less dense.

Earth, but less dense.

 They are balls of hydrogen, helium and They are balls of hydrogen, helium and methane

methane gas gas

 Inner layers are compressed into hot Inner layers are compressed into hot liquids, then a small solid core

liquids, then a small solid core

 All have All have multiple moons multiple moons and even and even rings rings . .

The Jovian Line-Up The Jovian Line-Up

 Jupiter was the supreme god in Roman Jupiter was the supreme god in Roman mythology.

mythology.

 Jupiter was also called “Jove” in Middle Jupiter was also called “Jove” in Middle English.

English.

 The planet Jupiter is the largest planet. The planet Jupiter is the largest planet.

 Jovian planets include Jupiter, Saturn, Jovian planets include Jupiter, Saturn, Uranus, and Neptune.

Uranus, and Neptune.

Stats Stats

Planet

Planet Mass (kg)

Radius (mi)

Gravity ^Rotation

(day)

Temp.

(˚C) Earth

Earth ^{6.0x10 6.0x10}

3,968 3,968 1.00 1.00 1.00 1.00 ^{7.2 7.2}

(45˚F) (45˚F)

Jupiter

Jupiter ^{1.9x10 1.9x10}

44,020 14 14 0.41 0.41 ^{-145 -145} Saturn

Saturn ^{5.7x10 5.7x10}

37,200 0.7 0.7 0.43 0.43 ^{-175 -175} Uranus

Uranus ^{8.8x10 8.8x10}

16,120 0.7 0.7 -0.72 -0.72 ^{-224 -224} Neptune

Neptune ^{1.0x10 1.0x10}

15,500 0.4 0.4 0.67 0.67 ^{-218 -218}

Stats Stats

 Jupiter and Saturn have Jupiter and Saturn have the most in common with the most in common with

each other.

each other.

 Both are Both are HUGE HUGE with their with their bulk consisting mainly of bulk consisting mainly of

hydrogen and helium.

hydrogen and helium.

 Uranus and Neptune are Uranus and Neptune are both much larger than both much larger than

Earth, but they are less Earth, but they are less

than half the diameter of than half the diameter of

Jupiter and Saturn.

Jupiter and Saturn.

Density Density

 Density = Density =

mass/volume (g/cm mass/volume (g/cm

) )

 Earth: 5.5 Earth: 5.5

 Jupiter: 1.3 Jupiter: 1.3

 Saturn: .71 Saturn: .71

 Uranus: 1.2 Uranus: 1.2

 Neptune: 1.6 Neptune: 1.6

Why is Earth so much more dense?

More Jovian Stats More Jovian Stats

 All of the jovian planets have thick All of the jovian planets have thick

‘atmospheres’ of hydrogen and helium of hydrogen and helium

covering a super dense core slightly larger covering a super dense core slightly larger

than Earth or Venus.

than Earth or Venus.

 Their atmospheres are ancient and they’ve Their atmospheres are ancient and they’ve probably changed little since early in the

probably changed little since early in the lifetime of the solar system.

lifetime of the solar system.

 Strong gravity Strong gravity holds on to the holds on to the atmospheres.

atmospheres.

Surface Conditions??

Surface Conditions??

 On Earth we have the sky above and the ground On Earth we have the sky above and the ground below.

below.

 On the jovian planets, the gaseous atmosphere On the jovian planets, the gaseous atmosphere never really ends. It just becomes denser with never really ends. It just becomes denser with

depth.

depth.

 They don’t have a solid surface! They don’t have a solid surface!

 As the pressure becomes greater, the gases As the pressure becomes greater, the gases

become more dense, they become liquid, which become more dense, they become liquid, which

is presumably what lies at the core of these is presumably what lies at the core of these

planets.

planets.

Rocky Conditions Rocky Conditions

 When astronomers speak of the “rocky” When astronomers speak of the “rocky”

cores of these planets, they’re referring to cores of these planets, they’re referring to chemical composition rather than physical chemical composition rather than physical

state.

state.

 Pressures are so great at the cores of Pressures are so great at the cores of

Jupiter and Saturn that even the element Jupiter and Saturn that even the element

hydrogen takes on a liquid metallic form.

hydrogen takes on a liquid metallic form.

Latecomers Latecomers



Since ancient times, the Since ancient times, the inventory of the solar inventory of the solar

system was seemingly system was seemingly

clear: Earth, Mercury, clear: Earth, Mercury,

Venus, Mars, Jupiter, and Venus, Mars, Jupiter, and

Saturn.

Saturn.



It wasn’t until 1781 that It wasn’t until 1781 that Uranus and Neptune Uranus and Neptune

were discovered.

were discovered.



It was Uranus’ “irregular” It was Uranus’ “irregular”

orbit and Newton’s law of orbit and Newton’s law of

gravity that lead us to gravity that lead us to

Neptune.

Neptune.

Uranus Uranus

 Uranus will appear as a Uranus will appear as a greenish

greenish disk, probably disk, probably featureless.

featureless.

 With a good telescope With a good telescope you might be able to see you might be able to see

atmospheric features and atmospheric features and

bright spots.

bright spots.

 Could even see Titania Could even see Titania and Oberon, Uranus’ two and Oberon, Uranus’ two

largest moons.

largest moons.

Neptune Neptune

 Even advanced Even advanced

amateur astronomers amateur astronomers

have not seen have not seen

Neptune.

Neptune.

 It will be It will be blue blue in color in color and featureless.

and featureless.

Aptly named after the Aptly named after the

god of the sea.

god of the sea.

Earthbound Views: Jupiter and Earthbound Views: Jupiter and

Saturn Saturn

 Jupiter and Saturn are very easily viewed. Jupiter and Saturn are very easily viewed.

 Even a modest telescope will reveal Even a modest telescope will reveal

Saturn’s rings and Jupiter’s atmospheric Saturn’s rings and Jupiter’s atmospheric

rings.

rings.

 Jupiter rotates so fast you could even Jupiter rotates so fast you could even watch details move across the face.

watch details move across the face.

 Saturn is a spectacular object to view with Saturn is a spectacular object to view with its rings and 9 moons.

its rings and 9 moons.

Views from

Views from Voyager Voyager and and Galileo Galileo

 Space probes sent back Space probes sent back unprecedented images of unprecedented images of

the jovian planets.

the jovian planets.

 The Voyager The missions missions revealed volcanic activity revealed volcanic activity on Io on , one of Jupiter’s , one of Jupiter’s

moons.

moons.

 Also discovered another Also discovered another system of rings around system of rings around

Jupiter and 10 additional Jupiter and 10 additional

moons around Uranus

moons around Uranus

( ( ~15). ~15).

Views from

Views from Voyager Voyager and and Galileo Galileo

 Discovered three Discovered three

planetary rings and six planetary rings and six

previously unknown previously unknown

moons.

moons.

 The “featureless” surface The “featureless” surface of Neptune was finally of Neptune was finally

resolved into bands and resolved into bands and

giant cloud streaks.

giant cloud streaks.

 Some of Saturn’s rings Some of Saturn’s rings rotate backwards!

rotate backwards!

Rotation:

Rotation: A New Twist A New Twist

 It’s actually very difficult to calculate the It’s actually very difficult to calculate the rotation rates of the gaseous planets.

rotation rates of the gaseous planets.

 Because there is no solid surface, different Because there is no solid surface, different parts at the surface will rotate at different parts at the surface will rotate at different

rates.

rates.

 The true rotation rate is calculated using The true rotation rate is calculated using the fluctuations of radio emissions.

the fluctuations of radio emissions.

Tilt: A New Twist Tilt: A New Twist

 Neptune and Saturn are Neptune and Saturn are tilted tilted on their on their axes similar to Earth (~23˚)

axes similar to Earth (~23˚)

 Jupiter is only tipped 3 degrees. Jupiter is only tipped 3 degrees.

 Uranus has to be the extremist. It is tilted Uranus has to be the extremist. It is tilted 98 degrees , essentially lying on its side! , essentially lying on its side!

 Has the most extreme seasonal changes Has the most extreme seasonal changes in the solar system.

in the solar system.

Stormy Weather Stormy Weather

 Jupiter’s spectacular surface features indicate Jupiter’s spectacular surface features indicate a turbulent atmosphere.

a turbulent atmosphere.

 Jupiter’s Jupiter’s atmosphere is arranged in distinct atmosphere is arranged in distinct layers. (like Earth)

layers. (like Earth)

 The bands of wind flow east and west called The bands of wind flow east and west called zonal flow

zonal flow , ,

 There are also many smaller-scale weather There are also many smaller-scale weather patterns.

patterns.

 The Great Red Spot is a giant storm The Great Red Spot is a giant storm

The Great Red Spot The Great Red Spot

 The Great Red Spot The Great Red Spot was first reported by was first reported by

Robert Hooke.

Robert Hooke.

 It is a storm, a It is a storm, a

swirling hurricane or swirling hurricane or whirlpool, of gigantic whirlpool, of gigantic

dimensions.

dimensions.

 It’s twice the size of It’s twice the size of Earth!! On top of the Earth!! On top of the

size, it’s almost 300 size, it’s almost 300

years old!!

years old!!

The Great Red Spot The Great Red Spot

 It rotates once every It rotates once every six days and is

six days and is

accompanied by other accompanied by other

smaller storms.

smaller storms.

 Neptune has a similar Neptune has a similar storm called the Great storm called the Great

Dark Spot.

Dark Spot.

The Great Red Spot The Great Red Spot

 How could a storm last for so long? How could a storm last for so long?

 Hurricanes on Earth are disrupted by land Hurricanes on Earth are disrupted by land masses. But there are is no land on

masses. But there are is no land on Jupiter to disrupt the storm.

Jupiter to disrupt the storm.

 It will only be disrupted if another storm It will only be disrupted if another storm does so.

does so.

Bands of Atmosphere Bands of Atmosphere

 The atmospheric bands that are Jupiter’s are The atmospheric bands that are Jupiter’s are the result of

the result of convective motion convective motion and zonal wind and zonal wind patterns.

patterns.

 Warm gas rises, while Warm gas rises, while cool gases sink. cool gases sink.

 The wind speed on The wind speed on

Jupiter vary with latitude. Jupiter vary with latitude.

Saturn Atmosphere Saturn Atmosphere

 Saturn’s atmosphere Saturn’s atmosphere is similar to Jupiter’s, is similar to Jupiter’s, mostly hydrogen and mostly hydrogen and

helium.

helium.

 Weaker gravity Weaker gravity results in thicker results in thicker

cloud layers that give cloud layers that give

the planet a more the planet a more

uniform appearance.

uniform appearance.

Atmospheres of Uranus and Atmospheres of Uranus and

Neptune Neptune

 These atmospheres have not been probed These atmospheres have not been probed by unmanned space probes.

by unmanned space probes.

 We have studied them spectroscopically We have studied them spectroscopically from Earth.

from Earth.

 Mostly hydrogen and helium (again). Mostly hydrogen and helium (again).

 Ammonia is far less abundant on these Ammonia is far less abundant on these two planets than on Jupiter and Saturn.

two planets than on Jupiter and Saturn.

Atmospheres of Uranus and Atmospheres of Uranus and

Neptune Neptune

 Any ammonia present is frozen because of Any ammonia present is frozen because of lower pressures.

lower pressures.

 The lack of ammonia and the presence of The lack of ammonia and the presence of methane give these planets a blueish

methane give these planets a blueish appearance.

appearance.

 Uranus has less methane so it looks blue- Uranus has less methane so it looks blue- green, while Neptune looks very blue.

green, while Neptune looks very blue.

Inside the Jovians Inside the Jovians

 Uranus and Neptune are believed to have Uranus and Neptune are believed to have rocky cores similar in size to those of

rocky cores similar in size to those of Jupiter and Saturn.

Jupiter and Saturn.

 Cores are surrounded by a slushy layer Cores are surrounded by a slushy layer consisting of water clouds and perhaps consisting of water clouds and perhaps

ammonia.

ammonia.