The Jovian Planets, Part IIIThe Jovian Planets, Part III

Uranus and NeptuneUranus and Neptune

URANUSURANUSThe God of the HeavensThe God of the Heavens

Physical DataPhysical Data

Discovered by William Herschel in 1781Discovered by William Herschel in 1781 Diameter: 51,118 km (4.01 DDiameter: 51,118 km (4.01 Dearthearth))

Mass: 8.69x10Mass: 8.69x102525 kg (14.54 M kg (14.54 Mearthearth))

Density: 1.24 g/cmDensity: 1.24 g/cm33

Rotation Period: 17.24 hoursRotation Period: 17.24 hours Tilt of Axis: 98Tilt of Axis: 98oo (retrograde rotation!) (retrograde rotation!) Surface Temperature: 52 K (-366Surface Temperature: 52 K (-366oo F) F)

Physical DataPhysical Data

Orbital Semi-Major Axis: 19.18 AUOrbital Semi-Major Axis: 19.18 AU Orbital Period: 84.01 yearsOrbital Period: 84.01 years Orbital Inclination: 0.8Orbital Inclination: 0.8oo

Orbital Eccentricity: 0.047Orbital Eccentricity: 0.047 Surface Gravity: 0.919 Earth gravitySurface Gravity: 0.919 Earth gravity Satellites: 27 as of 2011Satellites: 27 as of 2011 Magnetic Field: yesMagnetic Field: yes

Uranus’ InteriorUranus’ Interior

ATMOSPHEREMOLECULAR HYDROGEN

ICE

ROCK

The Discovery of UranusThe Discovery of Uranus

First discovered planet First discovered planet even though at its even though at its closest to earth it can be closest to earth it can be seen with the naked eyeseen with the naked eye

Was recorded 22 times Was recorded 22 times as a star on star charts as a star on star charts before W. Herschel before W. Herschel discovered it as a planet discovered it as a planet in 1781in 1781

m

Uranus’ MotionsUranus’ Motions

N

N

N

N

S

S

S

S

SUN

Uranus rotates on its side, producing strangeseasons and day-night patterns

Uranus’ AtmosphereUranus’ Atmosphere

COMPOSITION:COMPOSITION: 85% Hydrogen85% Hydrogen 15% Helium15% Helium Traces of MethaneTraces of Methane

CLOUDS:CLOUDS: Mostly made of methane iceMostly made of methane ice Featureless cloudtops (inconspicous bands)Featureless cloudtops (inconspicous bands)

Uranus’ Magnetic FieldUranus’ Magnetic Field

Magnetic dipole is Magnetic dipole is offset 31% from the offset 31% from the center of the planetcenter of the planet

Tilted -59Tilted -59oo from from rotational axisrotational axis

Comparable in strength Comparable in strength to Earth’s (0.74 Earth’s)to Earth’s (0.74 Earth’s)

Uranus has aurora and Uranus has aurora and radio emissionsradio emissions

Uranus’ RingsUranus’ Rings

Found from star Found from star occultations in 1977occultations in 1977

Thought to be made Thought to be made of stoneof stone

Uranus also has Uranus also has partial rings called partial rings called “ring arcs”“ring arcs”

Also has sheperd Also has sheperd satellitessatellites

Uranus’ MoonsUranus’ Moons

All are named after William Shakespeare All are named after William Shakespeare and Alexander Pope charactersand Alexander Pope characters

There are 15 known moonsThere are 15 known moons

Uranus’ MoonsUranus’ Moons

MIRANDA:MIRANDA: Surface is a weird mix of Surface is a weird mix of

old and new terrainold and new terrain It has been proposed It has been proposed

than it was shattered and than it was shattered and reassembled in this wayreassembled in this way

There was not enough There was not enough heat to fuse it smoothly heat to fuse it smoothly togethertogether

m

Uranus’ MoonsUranus’ Moons

ARIEL:ARIEL: Youngest surface of Youngest surface of

the Uranian Satellitesthe Uranian Satellites There is evidence of There is evidence of

tectonic activitytectonic activity It has faults over 10 It has faults over 10

km deepkm deep

Uranus’ MoonsUranus’ Moons

TITANIA:TITANIA: Largest of Uranus’ Largest of Uranus’

moonsmoons Has faults up to 100 Has faults up to 100

km acrosskm across Has a heavily cratered Has a heavily cratered

surfacesurface

NEPTUNENEPTUNEGOD OF THE SEAGOD OF THE SEA

Physical DataPhysical Data

First observed in 1846 by Johann GalleFirst observed in 1846 by Johann Galle Diameter: 49,500 km (3.89 DDiameter: 49,500 km (3.89 Dearthearth))

Mass: 1.030x10Mass: 1.030x102626 kg (17.23 M kg (17.23 Mearthearth) )

Density: 1.61 g/cmDensity: 1.61 g/cm33

Rotation Period: 16.11 hoursRotation Period: 16.11 hours Tilt of Axis: 28.76Tilt of Axis: 28.76oo

Surface Temperature: 57 K (-357Surface Temperature: 57 K (-357oo F) F)

Physical DataPhysical Data

Orbital Semi-Major Axis: 30.06 AUOrbital Semi-Major Axis: 30.06 AU Orbital Period: 164.79 yearsOrbital Period: 164.79 years Orbital Inclination: 1.8Orbital Inclination: 1.8oo

Orbital Eccentricity: 0.009Orbital Eccentricity: 0.009 Surface Gravity: 1.19 Earth’s gravitySurface Gravity: 1.19 Earth’s gravity Satellites: 13 as of 2011Satellites: 13 as of 2011 Magnetic Field: yesMagnetic Field: yes

The Discovery of NeptuneThe Discovery of Neptune

It’s existence was calculated before it was It’s existence was calculated before it was observed from variations of Uranus’ orbit from observed from variations of Uranus’ orbit from what was predictedwhat was predicted

Calculations were made by U.J. Leverrier, sent to Calculations were made by U.J. Leverrier, sent to Johann Galle at Berlin Observatory, and he found Johann Galle at Berlin Observatory, and he found Neptune after searching for 30 minutesNeptune after searching for 30 minutes

Galileo actually recorded Neptune twice in 1612 Galileo actually recorded Neptune twice in 1612 and 1613 in his notebooks as a background star in and 1613 in his notebooks as a background star in his drawings of Jupiterhis drawings of Jupiter

Neptune’s InteriorNeptune’s Interior

ATMOSPHERE

MOLECULAR HYDROGEN

ICE

ROCK

Similar to Uranus

Neptune’s AtmosphereNeptune’s Atmosphere

75% Hydrogen75% Hydrogen 25% Helium25% Helium Small amounts of: Methane, Ammonia &Small amounts of: Methane, Ammonia &

AcetyleneAcetylene

There are three majors cloud-top features:There are three majors cloud-top features:The Great Dark SpotThe Great Dark SpotDark Spot 2Dark Spot 2ScooterScooter

Neptune’s AtmosphereNeptune’s Atmosphere

The Great Dark Spot:The Great Dark Spot: Anti-cyclone with a Anti-cyclone with a

circulation period of circulation period of 16 days16 days

About the size of About the size of EarthEarth

In southern In southern hemispherehemisphere

Neptune’s AtmosphereNeptune’s Atmosphere

Dark Spot 2:Dark Spot 2: Smaller cyclone in S. Smaller cyclone in S.

hemisperehemispere

Scooter:Scooter: Fast rotatingFast rotating Rapidly changes shape Rapidly changes shape

Great Dark Spot

Scooter

Dark Spot 2

Neptune’s Magnetic FieldNeptune’s Magnetic Field

Magnetic dipole is Magnetic dipole is offset 55% from center offset 55% from center of Neptuneof Neptune

Tilted -47Tilted -47oo with with respect to rotational respect to rotational axisaxis

Has a field strength of Has a field strength of 0.4x Earth’s at the 0.4x Earth’s at the equatorequator

Has aurora and radio Has aurora and radio emissionsemissions

Neptune’s RingsNeptune’s Rings

Discovered in 1981Discovered in 1981 Brighter areas are ring Brighter areas are ring

arcsarcs There is a total of 5 There is a total of 5

rings, all very thinrings, all very thin

Neptune’s MoonsNeptune’s Moons

TRITON:TRITON: Has thin atmosphere, Has thin atmosphere,

geysers, and strange geysers, and strange “cantaloupe terrain”“cantaloupe terrain”

Diameter: 3000kmDiameter: 3000km

Neptune’s MoonsNeptune’s Moons

Proteus:Proteus: Second largest moon Second largest moon

of Neptune discovered of Neptune discovered by Voyagerby Voyager

Surprisingly, Neried, Surprisingly, Neried, Neptune’s third largest Neptune’s third largest moon was discovered moon was discovered from the ground from the ground before Proteusbefore Proteus