Download - Lecture 11: The Giant (or Jovian) Planets

Lecture 11:Lecture 11:The Giant (or Jovian) PlanetsThe Giant (or Jovian) Planets

Claire MaxClaire MaxNovember 2, 2010November 2, 2010

Astro 18: Planets and Planetary Astro 18: Planets and Planetary SystemsSystems

UC Santa CruzUC Santa Cruz

Jupiter’s Great Red Spot

Public lecture on finding Public lecture on finding earth-like planets with the earth-like planets with the Kepler spacecraftKepler spacecraft

• Wednesday, Nov. 17th, 2010, at 7 pmWednesday, Nov. 17th, 2010, at 7 pm

• Astronomer Natalie Batalha from San Astronomer Natalie Batalha from San Jose State UniversityJose State University

• Catching Shadows: Kepler's Search for Catching Shadows: Kepler's Search for New WorldsNew Worlds

• Smithwick Theater, Foothill College, El Smithwick Theater, Foothill College, El Monte Road and Freeway 280,in Los Monte Road and Freeway 280,in Los Altos Hills, California.Altos Hills, California.

• Parking on campus costs $2. Call 650-Parking on campus costs $2. Call 650-949-7888 for more information and 949-7888 for more information and driving directions.driving directions.

The Giant Planets in our own The Giant Planets in our own Solar SystemSolar System

• Jupiter, Saturn, Uranus, Neptune Jupiter, Saturn, Uranus, Neptune (and Earth for comparison)(and Earth for comparison)

Outline of lectureOutline of lecture

• Jovian Planets:Jovian Planets:

– PropertiesProperties

– FormationFormation

– Interior structureInterior structure

– AtmospheresAtmospheres

The Jovian Worlds: The Jovian Worlds: A Different Kind of Planet A Different Kind of Planet

• Briefly describe the major features of Briefly describe the major features of the Jovian planets.the Jovian planets.

• Why are Jovian planets so different Why are Jovian planets so different from terrestrial planets?from terrestrial planets?

Goals for learning:Goals for learning:

Jovian Planet PropertiesJovian Planet Properties

• Compared to the terrestrial planets, Compared to the terrestrial planets, the Jovians:the Jovians:– are much larger & more massiveare much larger & more massive– are composed mostly of Hydrogen, are composed mostly of Hydrogen,

Helium, & Hydrogen compoundsHelium, & Hydrogen compounds– have no solid surfaceshave no solid surfaces– rotate more quicklyrotate more quickly– have slightly “squashed” shapeshave slightly “squashed” shapes– have ring systemshave ring systems– have many moonshave many moons

Jupiter318x Earth

Jupiter’s 4 Galilean Moons

Saturn95x Earth

Uranus14x Earth

Neptune17x Earth

Why are the Jovian Planets so Different?Why are the Jovian Planets so Different?

• They formed beyond the frost line to form large, They formed beyond the frost line to form large, icy planetesimals which were massive enough to… icy planetesimals which were massive enough to… – Capture H/He far from Sun to form gaseous planets.Capture H/He far from Sun to form gaseous planets.– Each Jovian planet formed its own “miniature” solar Each Jovian planet formed its own “miniature” solar

nebula.nebula.– Moons formed out of these disks.Moons formed out of these disks.

What are the distinguishing What are the distinguishing features of the Giant Planets?features of the Giant Planets?

• Big puffy gas balls!Big puffy gas balls!– No solid surface, in contrast with terrestrial planetsNo solid surface, in contrast with terrestrial planets

• Mostly hydrogen and heliumMostly hydrogen and helium– Terrestrial planets are made of rocks - little H and Terrestrial planets are made of rocks - little H and

HeHe– Because of small mass, low gravity, of terrestrial Because of small mass, low gravity, of terrestrial

planets, light elements like H, He escaped to spaceplanets, light elements like H, He escaped to space

• Giant Planets are farther from Sun Giant Planets are farther from Sun – Beyond the “ice line” in the early Solar SystemBeyond the “ice line” in the early Solar System– Water and other hydrogen compounds were solidWater and other hydrogen compounds were solid– Allowed higher-mass objects to form by accretionAllowed higher-mass objects to form by accretion

Difference between a Giant Difference between a Giant Planet and a star?Planet and a star?

• Stars get their heat from nuclear Stars get their heat from nuclear fusionfusion– Four hydrogen atoms fuse to form a helium atomFour hydrogen atoms fuse to form a helium atom

+ +

+ +

• To make hydrogen To make hydrogen atoms move fast, need atoms move fast, need high temperatures in high temperatures in core of starcore of star

• The more massive a The more massive a ball of gas is, the ball of gas is, the hotter its corehotter its core

• Don’t get any fusion Don’t get any fusion for masses < 13 -14 for masses < 13 -14 MMJupiterJupiter

More about stars and fusion More about stars and fusion energyenergy

• Giant Planets (M < 13 Mj): no nuclear fusion Giant Planets (M < 13 Mj): no nuclear fusion energyenergy

– Not enough mass lying over core to create high Not enough mass lying over core to create high temperatures in centertemperatures in center

• Stars: how does nuclear fusion release energy?Stars: how does nuclear fusion release energy?

• Einstein explained it all!Einstein explained it all!– Helium is a bit Helium is a bit lessless than four times as heavy as than four times as heavy as

hydrogenhydrogen– Difference in mass: Difference in mass: ΔΔm = 4mm = 4mHH - m - mHeHe

– By Einstein’s famous rule, mass difference is released By Einstein’s famous rule, mass difference is released as energy:as energy: E = E = ΔΔm cm c22

• This “mass energy” keeps to core of a star hot, This “mass energy” keeps to core of a star hot, until it has “fused” all its hydrogenuntil it has “fused” all its hydrogen

Distances of Giant Planets Distances of Giant Planets from Sunfrom Sun

• EarthEarth 1 AU1 AU

• JupiterJupiter 5.2 AU5.2 AU

• SaturnSaturn 9.5 AU9.5 AU

• UranusUranus 19 AU19 AU

• NeptuneNeptune 30 AU30 AU

Five times farther from Sun

30 times farther from Sun!

Jovian Planet CompositionJovian Planet Composition

• Jupiter and SaturnJupiter and Saturn– Mostly H and He gasMostly H and He gas

• Uranus and NeptuneUranus and Neptune– Mostly hydrogen compounds: water Mostly hydrogen compounds: water

(H(H22O), methane (CHO), methane (CH44), ammonia (NH), ammonia (NH33))– Some H, He, and rockSome H, He, and rock

Jovian Planet Interiors Jovian Planet Interiors

• Briefly describe the interior Briefly describe the interior structure of Jupiter.structure of Jupiter.

• Why is Saturn almost as big in Why is Saturn almost as big in radius as Jupiter?radius as Jupiter?

• How do the Jovian planet interiors How do the Jovian planet interiors differ, and why?differ, and why?


Interiors: qualitative Interiors: qualitative descriptiondescription

• Mostly gases plus the odd forms of Mostly gases plus the odd forms of matter that are made when gases are matter that are made when gases are put under high pressureput under high pressure– Liquid hydrogen, metallic hydrogenLiquid hydrogen, metallic hydrogen

• It is probable (but not completely It is probable (but not completely proven yet) that all the Giant Planets proven yet) that all the Giant Planets have rocky cores at their centershave rocky cores at their centers– Accretion of matter to make planets started Accretion of matter to make planets started

with these rocky cores, then added iceswith these rocky cores, then added ices

Giant planets were farther from Giant planets were farther from early Sun than the “ice line” or early Sun than the “ice line” or “frost line”“frost line”

• Best estimate: “frost line” was between current Best estimate: “frost line” was between current orbits of Mars and Jupiterorbits of Mars and Jupiter

• Outside “frost line”: rocky cores could attract icy Outside “frost line”: rocky cores could attract icy solid material fast enough that planets were solid material fast enough that planets were already quite massive before early solar wind already quite massive before early solar wind blew gas nebula awayblew gas nebula away

or “ice line”

An unusually dense extrasolar planet

Inside the Jovian PlanetsInside the Jovian Planets

• All Jovian cores appear to be similar.All Jovian cores appear to be similar.

– made of rock, metal, and Hydrogen compoundsmade of rock, metal, and Hydrogen compounds

– about 10 x the mass of Earthabout 10 x the mass of Earth

• Uranus & Neptune captured less gas from the Solar nebula.Uranus & Neptune captured less gas from the Solar nebula.

– accretion of planetesimals took longeraccretion of planetesimals took longer

– not much time for gas capture before nebula was cleared out by not much time for gas capture before nebula was cleared out by Solar windSolar wind

• Only Jupiter and Saturn have high enough pressure for H & He Only Jupiter and Saturn have high enough pressure for H & He to exist in liquid and metallic states.to exist in liquid and metallic states.

Inside JupiterInside Jupiter

• Moving from the surface to Moving from the surface to the core:the core:– temperature increasestemperature increases– pressure & density increasespressure & density increases

• The core of Jupiter is slightly The core of Jupiter is slightly larger than Earth in size.larger than Earth in size.

• But it is 5 times as dense!But it is 5 times as dense!– thank to tremendous weight thank to tremendous weight

from abovefrom above

• So Jupiter's core has 10 So Jupiter's core has 10 times the mass of Earth.times the mass of Earth.

Although Jupiter has no solid surface and consists Although Jupiter has no solid surface and consists mostly of H & He, it does have distinct interior layers, mostly of H & He, it does have distinct interior layers, defined by defined by phasephase. .

More about Jupiter’s coreMore about Jupiter’s core

• ““Liquid metallic hydrogen”: a very Liquid metallic hydrogen”: a very unusual state of matter unusual state of matter ((“degenerate”“degenerate”). ).

• Predicted many years ago Predicted many years ago – Jupiter’s core has temperature of 25,000 K Jupiter’s core has temperature of 25,000 K

and pressure of 12 million bars -- 12 million and pressure of 12 million bars -- 12 million times as large as sea level pressure on the times as large as sea level pressure on the EarthEarth

• Such a state for hydrogen has now Such a state for hydrogen has now been reproduced in labs on Earth. been reproduced in labs on Earth.

How do we know this?How do we know this?

• Density ---> made of primarily light stuff Density ---> made of primarily light stuff ---> hydrogen and helium---> hydrogen and helium

– Jupiter: density 1.3 gm/ccJupiter: density 1.3 gm/cc– Saturn: density 0.7gm/ccSaturn: density 0.7gm/cc

• Magnetic fields ---> yes; all jovians have Magnetic fields ---> yes; all jovians have strong magnetic fields ---> molten, strong magnetic fields ---> molten, electrically conducting interiorselectrically conducting interiors

• Nonspherical shapes (flattening due to Nonspherical shapes (flattening due to rapid rotation) ---> interior structure ---> rapid rotation) ---> interior structure ---> rocky cores 5-20 x mass of the Earth rocky cores 5-20 x mass of the Earth (both Jupiter and Saturn) (both Jupiter and Saturn)

Liquid metallic hydrogen?Liquid metallic hydrogen?

• Liquid hydrogen: if you poured it into a Liquid hydrogen: if you poured it into a cup, it would assume the shape of the cup, cup, it would assume the shape of the cup, but would not spread out throughout the but would not spread out throughout the entire volume (as would a gas). entire volume (as would a gas).

• Metallic hydrogen: will conduct electricity. Metallic hydrogen: will conduct electricity.

• Fact that this layer can flow Fact that this layer can flow andand can can conduct electricity means that Jupiter and conduct electricity means that Jupiter and Saturn can support large internal Saturn can support large internal electrical currents and should thus show electrical currents and should thus show large magnetic fields.large magnetic fields.

All the Giant Planets except All the Giant Planets except Uranus are generating some of Uranus are generating some of their own heattheir own heat

• Jupiter, Saturn, Neptune radiate more Jupiter, Saturn, Neptune radiate more energy into space in infrared light than energy into space in infrared light than they receive from Sun in visible lightthey receive from Sun in visible light

• Reason: they are still contracting under Reason: they are still contracting under their own gravity!their own gravity!– Planet contracts or gets more centrally Planet contracts or gets more centrally

condensedcondensed– Material in core is squeezed, feels more Material in core is squeezed, feels more

pressurepressure– Temperature of core increasesTemperature of core increases– Additional heat conduction to outer parts of Additional heat conduction to outer parts of

planet, stronger infrared radiation to spaceplanet, stronger infrared radiation to space

Internal heat, continuedInternal heat, continued

• Another way to think about Another way to think about gravitational contraction making heatgravitational contraction making heat– Planet contractsPlanet contracts– Decreases its gravitational potential energy Decreases its gravitational potential energy

−− GmM/r GmM/r– Total energy = kinetic energy Total energy = kinetic energy −− GmM / r = GmM / r =

constantconstant– So kinetic energy must increaseSo kinetic energy must increase– Particles in core move faster (random Particles in core move faster (random

motions)motions)– Means their temperature is higherMeans their temperature is higher

Radii of Jupiter and SaturnRadii of Jupiter and Saturn

• Jupiter emits almost twice as much energy as it Jupiter emits almost twice as much energy as it absorbs from the Sun.absorbs from the Sun.– accretion, differentiation, radioactivity can not account accretion, differentiation, radioactivity can not account

for itfor it– Jupiter must still be contractingJupiter must still be contracting

• Jupiter has 3 x more mass than Saturn, but is not Jupiter has 3 x more mass than Saturn, but is not much larger!much larger!– the added weight of H & He compresses the core to a the added weight of H & He compresses the core to a

higher densityhigher density– just like stacking pillowsjust like stacking pillows

• If you added even more If you added even more mass, Jupiter would mass, Jupiter would get smaller.get smaller.

• Jupiter is about as Jupiter is about as large as a planet can large as a planet can get.get.

Very important spacecraftVery important spacecraft

• Voyager 1 and 2 (1980's)Voyager 1 and 2 (1980's)– Flew by Jupiter, Saturn, Uranus, NeptuneFlew by Jupiter, Saturn, Uranus, Neptune– First close-up views of all these planetsFirst close-up views of all these planets

• Galileo (recently ended mission)Galileo (recently ended mission)– In orbit around Jupiter for several yearsIn orbit around Jupiter for several years– Also sent a probe into Jupiter’s atmosphereAlso sent a probe into Jupiter’s atmosphere

• Cassini (in orbit around Saturn now, Cassini (in orbit around Saturn now, but passed by Jupiter)but passed by Jupiter)

Jovian Planet Atmospheres Jovian Planet Atmospheres

• How is Jupiter’s atmospheric structure How is Jupiter’s atmospheric structure similar to Earth’s?similar to Earth’s?

• Why does Jupiter have three distinct Why does Jupiter have three distinct cloud layers?cloud layers?

• What is the Great Red Spot?What is the Great Red Spot?

• How do other Jovian atmospheres How do other Jovian atmospheres compare to Jupiter’s?compare to Jupiter’s?


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Composition of atmospheres: Composition of atmospheres: mostly hydrogen and heliummostly hydrogen and helium

• Giant planets Giant planets are massive are massive enough that enough that light light elements (H, elements (H, He) didn’t He) didn’t entirely entirely escape to escape to space (as on space (as on Earth)Earth)

• This is very This is very similar to the similar to the Solar Solar composition!composition!

Atmospheres of the Giant Atmospheres of the Giant PlanetsPlanets

• Dominated by hydrogen and helium Dominated by hydrogen and helium gasesgases– Thus very different from terrestrial planetsThus very different from terrestrial planets– Earth’s atmosphere mostly nitrogenEarth’s atmosphere mostly nitrogen

• Clouds form out of this gaseous soup in Clouds form out of this gaseous soup in a variety of striking colorsa variety of striking colors

• Cloud patterns are organized by winds, Cloud patterns are organized by winds, which get their energy from the which get their energy from the planets’ internal heatplanets’ internal heat– By contrast, terrestrial planets’ weather is By contrast, terrestrial planets’ weather is

determined by heat from the Sundetermined by heat from the Sun

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Cloud bandsCloud bands

• Jupiter, Saturn clouds in Jupiter, Saturn clouds in fast-moving bandsfast-moving bands

• On Earth, transient On Earth, transient storms break up such storms break up such bands, but not on Jupiter bands, but not on Jupiter or Saturnor Saturn

• Storms on Jupiter can last Storms on Jupiter can last tens to hundreds of tens to hundreds of years!years!

• Why the cloud bands are Why the cloud bands are particular colors is not particular colors is not clear; color depends on clear; color depends on chemistry which we don’t chemistry which we don’t understand.understand.

Jupiter’s AtmosphereJupiter’s Atmosphere

• In 1995, the Galileo space In 1995, the Galileo space probe plunged into the probe plunged into the planet Jupiter!planet Jupiter!

• It measured the atmospheric It measured the atmospheric structure of Jupiterstructure of Jupiter– thermosphere thermosphere absorbs Solar X-absorbs Solar X-

raysrays– stratosphere stratosphere absorbs Solar UVabsorbs Solar UV– troposphere troposphere greenhouse gases greenhouse gases

trap heat from both Jupiter and trap heat from both Jupiter and the Sunthe Sun

• These are the same structures found in Earth’s These are the same structures found in Earth’s atmosphere.atmosphere.

• Atmospheres are governed by interactions between sunlight and Atmospheres are governed by interactions between sunlight and gases.gases.

Features on JupiterFeatures on Jupiter

• Credit: Imamura, U. OregonCredit: Imamura, U. Oregon

(c) Nick Strobel

Jupiter’s Cloud LayersJupiter’s Cloud Layers

• Convection in the troposphere Convection in the troposphere causes Jovian weather.causes Jovian weather.

• Warm gas rises to cooler Warm gas rises to cooler altitudes, where it condenses altitudes, where it condenses to form clouds.to form clouds.

• Three gases condense in the Three gases condense in the Jovian atmosphere:Jovian atmosphere:– ammonia (NHammonia (NH33))

– ammonium hydrosulfide ammonium hydrosulfide (NH(NH44SH)SH)

– water (Hwater (H22O)O)

• They condense at different They condense at different temperatures, so their clouds temperatures, so their clouds form at different altitudes.form at different altitudes.

Winds are strongly latitudinalWinds are strongly latitudinal

“Zonal winds” of alternating direction

Huge wind speeds on Saturn, Neptune

There are even opposing There are even opposing zonal winds at poles!zonal winds at poles!

What is the coriolis force?What is the coriolis force?

• Coriolis force: if you try to move radially in or Coriolis force: if you try to move radially in or out on a spinning merry-go-round, you are out on a spinning merry-go-round, you are deflected to the sidedeflected to the side

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• Like Earth, Jupiter Like Earth, Jupiter has circulation cells has circulation cells in its atmosphere.in its atmosphere.

• Jupiter is much Jupiter is much larger & rotates larger & rotates much faster.much faster.– Coriolis effect is Coriolis effect is

much strongermuch stronger

– circulation cells are circulation cells are split into many split into many bands of rising and bands of rising and falling airfalling air

– these are the these are the colored “stripes” we colored “stripes” we seesee

• Belts: warm, red, low Belts: warm, red, low altitudealtitude

• Zones: cool, white, Zones: cool, white, high altitude high altitude

What makes Jupiter's cloud bands so What makes Jupiter's cloud bands so colorful?colorful?

Visible light Infrared light

We also see high pressure storms We also see high pressure storms

• JupiterJupiter– the Great Red Spotthe Great Red Spot– we are not sure why it is redwe are not sure why it is red

• NeptuneNeptune– the Great Dark Spotthe Great Dark Spot

Jupiter Storms: best example Jupiter Storms: best example is the Great Red Spotis the Great Red Spot

• Great Red Great Red Spot has Spot has been around been around for at least for at least 300 yrs300 yrs– Seen in 17th Seen in 17th

century!century!

• A stable A stable vortexvortex

• Wind speeds Wind speeds >400 km/hr>400 km/hr

Another view of Another view of Jupiter’s Great Red Jupiter’s Great Red SpotSpot

• From Galileo spacecraftFrom Galileo spacecraft

Jupiter’s MagnetosphereJupiter’s Magnetosphere

• Jupiter’s strong magnetic field gives it an Jupiter’s strong magnetic field gives it an enormous magnetosphere.enormous magnetosphere.

• Gases escaping Io feed the donut-shaped Io torus.Gases escaping Io feed the donut-shaped Io torus.

Magnetospheres of other giant Magnetospheres of other giant planetsplanets

• All jovian All jovian planets have planets have substantial substantial magnetosphermagnetospheres, but es, but Jupiter’s is the Jupiter’s is the largest by far.largest by far.

Thought QuestionThought Question

Jupiter does Jupiter does not not have a large metal have a large metal core like the Earth. How can it have a core like the Earth. How can it have a magnetic field?magnetic field?

a) The magnetic field is left over from a) The magnetic field is left over from when Jupiter accreted.when Jupiter accreted.b) Its magnetic field comes from the Sun.b) Its magnetic field comes from the Sun.c) It has metallic hydrogen inside, which c) It has metallic hydrogen inside, which circulates and makes a magnetic field.circulates and makes a magnetic field.d) Its core creates a magnetic field, but it d) Its core creates a magnetic field, but it is very weak.is very weak.

Thought QuestionThought Question

Jupiter does Jupiter does not not have a large metal have a large metal core like the Earth. How can it have a core like the Earth. How can it have a magnetic field?magnetic field?

a) The magnetic field is left over from a) The magnetic field is left over from when Jupiter accreted.when Jupiter accreted.b) Its magnetic field comes from the Sun.b) Its magnetic field comes from the Sun.c) It has metallic hydrogen inside, which c) It has metallic hydrogen inside, which circulates and makes a magnetic field.circulates and makes a magnetic field. d) Its core creates a magnetic field, but it d) Its core creates a magnetic field, but it is very weak.is very weak.

Saturn has giant stormsSaturn has giant storms

• Outbreaks of Outbreaks of Saturn storms Saturn storms every ~30 yrsevery ~30 yrs

• Corresponds to Corresponds to summertime in summertime in Northern Northern HemisphereHemisphere– Not seen in S.Not seen in S.

• Origin of storms Origin of storms not yet not yet understoodunderstood

Neptune: Great Dark SpotNeptune: Great Dark Spot

• Lasted for Lasted for several several months as months as Voyager 2 Voyager 2 spacecraft spacecraft flew byflew by

• Wasn’t there a Wasn’t there a decade later decade later when Hubble when Hubble Space Space Telescope Telescope lookedlooked

Temperature structure of all Temperature structure of all the Giant Planet atmospheresthe Giant Planet atmospheres

Concept QuestionConcept Question

• On Earth, convection cells are formed On Earth, convection cells are formed when air is heated at the Earth's when air is heated at the Earth's surfacesurface

• What sources of heating might power What sources of heating might power convective cells on Jupiter?convective cells on Jupiter?

Why Uranus & Neptune are BlueWhy Uranus & Neptune are Blue

• They both have a higher They both have a higher fraction of methane gas.fraction of methane gas.– Methane absorbs red sunlight.Methane absorbs red sunlight.– Only blue light is reflected back Only blue light is reflected back

into space by the clouds.into space by the clouds.

• Uranus is “tipped” on its side.Uranus is “tipped” on its side.

• It should experience the most It should experience the most extreme seasonal changes.extreme seasonal changes.– no clouds or banded structure no clouds or banded structure

seen in 1986 when N pole facing seen in 1986 when N pole facing SunSun

– no weather, no internal heat?no weather, no internal heat?– HST saw storms in 1998, perhaps HST saw storms in 1998, perhaps

because the S hemisphere is because the S hemisphere is warming nowwarming now1986 - Visual 1998 - IR

Circumferential cloud bands seen by Circumferential cloud bands seen by Voyager spacecraft as it flew by Voyager spacecraft as it flew by NeptuneNeptune

• Linear features seen by Voyager in visible light were very thin

• Circumferential (followed lines of constant latitude)

• Similar in location and shape to the bands we see in infrared light

• Probably “pulled out” into circumferential shape by Neptune’s huge winds

Adaptive optics has been big Adaptive optics has been big help in studying Neptune from help in studying Neptune from the groundthe ground

Neptune in infrared lightwithout adaptive optics

Neptune in infrared light with Keck adaptive optics

Courtesy: L. SromovskyCourtesy: L. Sromovsky

Clouds and Rings of Uranus from Keck Telescope Adaptive Optics

Uranus, 3.8 “φ


• Uranus' year is 80 Earth-years longUranus' year is 80 Earth-years long

• The axis of rotation of Uranus lies almost The axis of rotation of Uranus lies almost in the plane of Uranus' orbit, so that the in the plane of Uranus' orbit, so that the planet "rolls its way around the Sun."planet "rolls its way around the Sun."

• As a consequence, seasons on Uranus As a consequence, seasons on Uranus arearea)a) As long as one Uranus yearAs long as one Uranus yearb)b) Non-existentNon-existentc)c) One fourth of Uranus' year, or about 20 Earth years One fourth of Uranus' year, or about 20 Earth years

longlongd)d) Four times Uranus' year, or about 320 Earth years longFour times Uranus' year, or about 320 Earth years long

The Main PointsThe Main Points

• Briefly describe major features of the Jovian Briefly describe major features of the Jovian planets.planets.

– Largely composed of hydrogen, helium, & hydrogen Largely composed of hydrogen, helium, & hydrogen compounds. No solid surfaces. Fast rotation. Slightly compounds. No solid surfaces. Fast rotation. Slightly “squashed” shapes. Many moons. Ring systems. “squashed” shapes. Many moons. Ring systems.

• Why are Jovian planets so different from Why are Jovian planets so different from terrestrial planets?terrestrial planets?

– Formed in cold, outer Solar System at the centers of Formed in cold, outer Solar System at the centers of “miniature protoplanetary disks.”“miniature protoplanetary disks.”

• Briefly describe the interior structure of Jupiter.Briefly describe the interior structure of Jupiter.– Central core of H compounds, rocks, & metals. Central core of H compounds, rocks, & metals. – Next layer up contains metallic H, followed by a layer of Next layer up contains metallic H, followed by a layer of

liquid H, followed by the gaseous atmosphere. liquid H, followed by the gaseous atmosphere. – Pressure, density, & temperature all increase with Pressure, density, & temperature all increase with

depth.depth.

The main points, continuedThe main points, continued

• Why is Saturn almost as big in radius as Why is Saturn almost as big in radius as Jupiter?Jupiter?

– Adding mass to a Jovian planet does not necessarily Adding mass to a Jovian planet does not necessarily increase its size, because the stronger gravity increase its size, because the stronger gravity compresses the mass to greater density. compresses the mass to greater density.

– Jupiter is near the maximum possible size for a Jovian Jupiter is near the maximum possible size for a Jovian planet.planet.

• How do the Jovian planet interiors differ, How do the Jovian planet interiors differ, and why?and why?

– All have cores of about the same mass, but differ in the All have cores of about the same mass, but differ in the amount of surrounding H and He. amount of surrounding H and He.

– Accretion took longer in the more spread out regions of Accretion took longer in the more spread out regions of the outer Solar System, so the more distant planets the outer Solar System, so the more distant planets captured less gas from the Solar nebula before it was captured less gas from the Solar nebula before it was blown away by the Solar wind.blown away by the Solar wind.

Main points, continuedMain points, continued

• How is Jupiter’s atmospheric structure How is Jupiter’s atmospheric structure similar to Earth’s?similar to Earth’s?

– Troposphere, stratosphere, and thermosphere Troposphere, stratosphere, and thermosphere created by similar interactions of gas and sunlight.created by similar interactions of gas and sunlight.

• Why does Jupiter have three distinct Why does Jupiter have three distinct cloud layers?cloud layers?

– Different gases condense at different temperatures. Different gases condense at different temperatures. Jupiter has three cloud layers, each at the altitude Jupiter has three cloud layers, each at the altitude where a particular gas can condense.where a particular gas can condense.

• What is the Great Red Spot?What is the Great Red Spot?– A giant, high-pressure storm.A giant, high-pressure storm.– Great Dark Spot on Neptune is probably similar.Great Dark Spot on Neptune is probably similar.

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