CH7 - Astronomy 1F03 2010/11 Fall Term 2010/11 Chaisson...

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Unformatted text preview: Astronomy 1F03 2010/11 Fall Term 2010/11 Chaisson & McMillan, Astronomy Chapter 7 The Jovian Planets The Giant Planets The Jupiter Jupiter Saturn Saturn Uranus Uranus Neptune Neptune History: History: Ancient Giants Ancient cultures knew about Jupiter and Saturn Visible with the naked eye from Earth Visible Various cultures had different names for the planets the Jupiter, Jove: Most Powerful Roman God God (similarities with Zeus) Saturn: Father of Jupiter Saturn: Observing Jupiter Observing Jupiter and it’s 4 Galilean Moons Jupiter Galilean are easily seen with a small telescope telescope The Great Red Spot and banded atmosphere have been observed for hundreds of years for Views from Earth Hubble Space Telescope Observing Saturn Saturn View from Earth Saturn with its rings has also been observed for hundreds of years observed Atmospheric Bands Atmospheric Rings including gaps Rings Hubble Space Hubble Telescope View Telescope Discovery of Uranus Discovery Uranus is just visible to the naked eye Uranus Uranus appears similar to a faint star Uranus (seen since 1690) Willam Herschel (1781) was the first to Willam (1781) realize Uranus was a new planet realize First planet discovered in recorded history First First name: “Georgium Sidus” Uranus was the father of Saturn Uranus Discovery of Neptune Discovery Uranus’ orbit was charted Uranus Uranus’ orbit could not be explained as a Uranus orbit simple Kepler ellipse unless there was a Kepler ellipse unless there new planet! new New Planet Theory: New John Adams (1845) John Urbain Leverrier (1846) Urbain First Observation: First Johann Galle (1846) Johann Observing Uranus & Neptune Uranus Uranus: Nearly featureless Neptune: Atmospheric Bands, clouds Atmospheric Great Dark Spot, now gone! Great “Like a blue Jupiter” Modern Observations: Modern Spacecraft Pioneer Pioneer Detailed Pictures: Voyager Probes (launched 1977,1979) Voyager Galileo Galileo Launched 1989, Jupiter: 1995-2003 Launched Dropped a probe into Jupiter’s atmosphere Dropped Cassini Cassini Launched 1997, Saturn: 2004 2004 Spacecraft: Spacecraft: All in the timing… Gravitational Slingshots used to adjust speed and direction of spacecraft spacecraft Entire missions pre-planned Entire Launch dates chosen to take advantage of slingshots advantage Spacecraft: Spacecraft: Voyager Missions The Jovian Planets: Overview The To Scale Giant Planets: Giant Mass Mass in the Solar System Sun 99.87% Sun Jupiter 0.10 % Jupiter Giant Planets: Giant Jupiter, Saturn, Neptune, Uranus 0.13 % Terrestrial Planets: Terrestrial Earth,Venus,Mars,Mercury: 0.001 % Giant Planets: Giant Rotation Angular Momentum in the Solar System: Sun 0.5 % Sun Jupiter more than 99 % Jupiter Jupiter contains most of the rotation left Jupiter from the early nebula from Mass & Density vs. Earth Mass Earth Jupiter Saturn Uranus Neptune Orbit 1 AU 5.2 AU 9.5 AU 19.2 AU 30 AU Mass 1 318 95 15 17 Radius 1 11.2 9.5 4.0 3.9 Density 5.5 g/ml 1.3 g/ml 0.7 g/ml 1.3 g/ml 1.6 g/ml Air: 0.001 g/ml Water Density: 1g/ml What are the Giant Planets made of? made Primarily Hydrogen and Helium Primarily The different densities come from how much the gas is compressed by gravity much Bigger planet, more compression Bigger Uranus and Neptune are denser: Uranus Substantial heavier material too Substantial Giant Planet Rotation Giant All the Jovian Planets rotate fast: All Jupiter (0.41 days), Saturn (0.43 days), Uranus (0.69 days), Neptune (0.72 days) Uranus’ axis is heavily tilted Uranus Giant Planet Seasons Giant Because of rotation axis tilt, like Earth, all the giant planets experience Seasons: Summer/Winter Seasons: Changing day lengths Changing Uranus has extreme Uranus seasons and days: Differential Rotation Differential Not all parts of the planets’ Not atmospheres rotate together: atmospheres Differential Rotation Differential E.g. Jupiter’s poles rotate slower E.g. poles than the equator than Interior rotation can be different too: Measured by rotation of magnetic field rotation Aside: Weather Aside: Planet Atmospheres All planets are heated most where the surface faces the sun most directly surface This heating makes gas move due to convection convection Convection cells take Convection the heat to the polar regions Coriolis Forces Coriolis Missile fired from the North Pole Aside: Weather Aside: Planet Atmospheres Rotation adds a twist: Rotation Coriolis Forces Coriolis Angular Momentum won’t Angular let the air flow straight north/south but bends it east/west instead east/west Competition between convection and rotation results in several smaller convection cells convection Bands Jupiter’s bands rotate at different rates: Jupiter bands Light zones, dark belts Light Digitally “rolled out” Cassini images Digitally Cassini Spacecraft Nov 2003 Jupiter Jupiter Jupiter’s Atmosphere Jupiter Colours result of Colours result complex chemistry depending on temperature temperature White Bands: Zones Dark Bands: Belts Dark Jupiter’s Atmosphere Jupiter Bands are results of intense convection Zones up Belts down Belts Jupiter’s rapid rotation Jupiter rapid keeps the bands narrow keeps Jupiter’s Jupiter Atmosphere Many layers of clouds Many Highest, cold clouds are white white Lower, warmer material is browner is Interior is very warm, high pressure high Galileo probe Entry point Aside: Fluid Motion Fluid Fluid (gas or liquid) moving in different directions is unstable to making ripples and vortices (sing. making sing. Vortex) along the edge Vortex Example: Wind over a lake makes Example: waves waves A vortex is a rotating patches of fluid: fluid: E.g. swirls in a river, cyclones in E.g. Earth’s atmosphere Earth Storms on Jupiter: Storms Spots Rotating systems can persist for a long time due to their angular momentum time On Earth, shallow atmosphere over land: On Hurricanes form over sea and decay over land Hurricanes On Jupiter it is gas most of the way down On The Great Red Spot is hundreds of years old The Saturn’s Appearance Saturn Banded like Jupiter Cassini 2004 Saturn’s Saturn Atmosphere False Colour False Colour Saturn spins rapidly like Jupiter and shows bands and spots and The upper whitish clouds are thicker: are Red colours are less Red colours are apparent apparent True colour Uranus’ Uranus Atmosphere Uranus has more methane Uranus Methane reflects primarily blue sunlight giving a blue tinge sunlight Uranus has relatively cold and featureless atmosphere – thick thick haze haze Some clouds Enhanced images Enhanced Neptune’s Neptune Atmosphere Neptune’s atmosphere Neptune atmosphere is very methane rich: deep blue deep Neptunes atmosphere is Neptunes atmosphere active with bands and spots spots The Great Dark Spot discovered in 1989 was gone in 1994 gone Great Dark Spot Infrared images Infrared showing hotter areas showing Jupiter’s Jupiter Interior Jupiter’s iinterior is so hot and dense that Jupiter nterior hydrogen liquifies liquifies At higher pressure it becomes metallic (conducting) (conducting) Jupiter may have a 10 Earth mass rocky core core Saturn’s Interior Saturn Saturn’s Interior is similar to Jupiter’s Saturn Less pressure, lower densities Less Smaller metallic hydrogen part Smaller Saturn probably has a 15 Earth mass core core Uranus & Uranus Neptune Uranus and Neptune have a substantial amount of ices (e.g Methane, Ammonia, Water) Water) At some depth, the atmospheres turn to icy slush icy Uranus and Neptune have rocky cores around 10 Earth masses around Magnetism Magnetism Auroras on Auroras Jupiter Jupiter All Jovian planets have strong Magnetic Fields strong Magnetic Field 1 20000 1000 100 100 Conducting Core Molten Iron Metallic Hydrogen Metallic Hydrogen Dissolved Ammonia? Dissolved Ammonia? Earth Jupiter Saturn Uranus Neptune Heat from the Giant Planets Heat Jupiter, Saturn and Neptune are all hotter than expected on the surface than They emit 2-3 times as much heat as they They times receive from the sun The Stefan-Boltzmann Law (Blackbody): The Boltzmann higher temperatures means more light energy emitted – they are hotter than equilibrium Internal Heating Internal Compressing gas to high pressure to form Compressing a gas planet heats it up gas Jupiter: Heat of formation still there Jupiter: Large planet takes longest to cool Large Saturn: Helium Rain Saturn: Uranus: Heat of formation gone Uranus: Neptune: Heat of formation still there Neptune: Methane clouds insulate the planet? Methane Saturn’s Helium Rain Saturn Saturn’s iinterior is high pressure but not as Saturn nterior hot as Jupiter hot Helium has formed raindrops: Helium 1/2 expected Helium gas seen in atmosphere Liquification and falling both release energy Liquification When the rain stops, Saturn will cool again When ...
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