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Lecture 15

Lecture 15--17, Study Guide


Department
Astronomy
Course Code
ASTA01H3
Professor
Rick Halpern
Lecture
15

Page:
of 5
Lecture 15: Jupiter
More than 2x mass of all planets in solar systems
1/1000th of sun mass
Orbits at 5.2 AU with 11.86 tropical years
3rd brightest object in sky
Not rocky
Rotation period calculated by observing rotation of magnetic field
9hr 55min Squashed by rotation but not as much as expected.
oCalculations tell us that this must be because Jupiter has a
dense
(rocky-type) core. About 10 Earth masses!!
oThe Atmosphere of Jupiter
Has bright zones had dark belts
Zones are cooler and higher than belts
Under zones and bands are stable flows called zonal
flow
The equator has highest wind speed
Shear of different velocity bands rolls up clouds layers
into rotating spots
Composition of Atmosphere
Mostly hydrogen and helium with trace
methane, ammonia and water vapor
Jupiter is mostly atmosphere
Color from chemical interactions
No solid surface so we take troposphere to be
0km
High wind speed at depth due to planets interior
heat
oGreat Red Spot
Has existed for 300 years
Spot bigger than earth
oIneternal Structure
Jupiter radiates more energy than it receives from the
sun
Core still cooling off from heating during gravitational
compression
Jupiter has to be 80 bigger to be considered a faint star
Center is rocky composition 10x size of the earth,
middle is metallic hydrogen and hydrogen and, top is
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molecular hydrogen
oMagnetosphere
Surrounded by belts of charged particles
30 million km across
Also has a plasma torus around caused by volcanoes in
Io
Magnetic field is tilted relative to rotation axis
This field strength is 20 000 times earths
Goes beyond staurn
Bigger than the sun
oMoons of Jupiter
63 moons most very small
16 have radii more than 10km
Some have retrograde orbits, some in clusters
4 bigger Galilean moons: Io, Europa, Ganymede,
Callisto
Orbits closer to jupter than other satellites
Similar to terrestrial planets
Low eccentricity
Largest is larger than Mercury
oGanymede
Density decreases as distance increases from
Jupiter
oLike mini solar system
Io
oVolcanoes active due to tidal forces
oRocky mantle
oIron/sulfide core
Europa
oIcy crust
oWater
oRocky mantle
oIron sulfide core
Ganymede
oIcy crust
oRocky mantle
oIron/sulfide cire
Callisto
oIce/rock mixture only (not differentiated)
Lecture 16: Moons of Jupiter
oIo
oDensest of jupiters moons
oMost geologically active in solar system
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oMany active volcanoes (400)
oSurface features change in few weeks
oNo craters because lava fills it up
oOrbital period 1.77days
oOrange Colour from sulfur
oVolcanism due to gravity and tidal forces
oCant become locked b/c other moons tugs
oEuropa
oNo crater
oSurface water ice
oTidal forces crack the ice, water flows from cracks keeping
surface relatively flat
oOrbital period 3.55 days
oVery weak magnetic field
oReflective surface, 64% of light it receives it reflects
oGanymede
oLargest moon in solar system
Larger than Pluto and mercury
oSimilar to moon but water ice, instead of lunar rock
oLight region is erupted ice material and younger than dark
surface
oLight spots are recent impact craters, icy material ejected
oMay have plate tectonics
oCallisto
oIcy and similar size as Ganymede but shows no evidence of
tectonics
oHeavily cratered
oValhalla large impact site
oMoons of Saturn
o30 Moons, 13 are greater than 100km
oWater icey but so cold that ice is hard as rock
oBesides small moons Saturn has 6 midsized moons Mimas,
Encledus, Tethys, Dione, Rhea and Iapetus
o1 Large moon Titan almost as large as Ganymede
oEnceladus
Icy geysers/volcanoes due to tidal forces
Most reflective in SS
oMimas
Small moon featuring a huge crater named Hershal
oTitan
Atmosphere more thicker and denser than Earths
Mostly nitrogen and argon
Lots of hydrocarbons
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