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Lecture

AS101 Lecture Notes - Roche Limit, Methane, Orbital Period


Department
Astronomy
Course Code
AS101
Professor
Patrick Mc Graw

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AS101 Week 11 Lecture 1
Common Characteristics of Jovian Planets
Larger than terrestrial planets.
Contain a lot more hydrogen and helium, and hydrogen-containing compounds like
water, ammonia, methane (a.k.a. “ices”)
Multiple satellites (some with atmospheres/oceans.)
All have rings made up of icy/rocky debris. (Saturn's are the most prominent.)
In summary, you could almost say that it's as if each one of the Jovian planets forms its
own miniature solar system.
Jupiter
Distance from Sun: 5.2 au
Orbital period: 11.86 years
Rotation period: 10 hours
Surface temp (top of cloud layer): -108 C
90%hydrogen, 10% helium, less than 1% other stuff.
Moons of Jupiter
The 4 Galilean moons
IO
Europa
Ganymede
Callisto
Moons of Jupiter: Other Moons
Many smaller objects (less than a few hundred km across) orbit Jupiter.
Closer than the Galilean four include Amalthea, Metis, Adrastea, Thebe.
Jupiter: Internal Structure
Metallic Hydrogen: Under high
pressures, hydrogen becomes an
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electrical conductor and behaves
like a liquid metal.
Liquid metal creates an extremely
strong magnetic field compared
to Earth.
Not naturally occurring on Earth, but under high pressures you can duplicate this
behaviour
Helps explain why Jupiter has such a high magnetic field
Jupiter's Aurora
Jupiter has an aurora because of its magnetic field
Jovian Weather: Belt and Zone Ciculation
Belts: darker bands of lower pressure.
Zones: lighter bands of higher pressure.
Patterns of wind can be understood based on the interaction of convection and the
planet's rotation, much as on Earth.
Convection: a pattern of circulation in which a fluid (or gas) heated from below rises,
then loses some of its heat and sinks.
o Convection is combined with planets rotation
o Convection: hotter gas to rise, cooler gas to sink
Earth's and Jupiter's Weather Similarities
Wind patterns created by the combination of convection, pressure differences and the
planet's rotation.
Winds spiral around high and low pressure areas due to the Coriolis effect.
Large-scale bands parallel to latitude lines, smaller systems within the global pattern.
Earth's and Jupiter's Weather Differences
Jupiter rotates faster, so the effect of rotation is stronger.
Jupiter is more symmetrical: no continents, oceans, mountain ranges to break up the
pattern. (And weaker seasonal changes.)
Main energy source on Earth is heat from the sun. On Jupiter, weather patterns are
mostly driven by heat escaping from the planet's interior.
Seasonal changes in Jupiter are weaker
Jupiter's Hot Interior
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