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A Solar System within
a Solar System
Physical Properties
Earth Jupiter• Mass 1 318
kg 5.97x1024
1.899x1027
Physical Properties
Earth Jupiter• Radius 1 11.2
equatorial 6378 71,492
polar 6357 66,854
• Oblateness 0.003 0.065
Equatorial radius – polar radius Equatorial radius
Physical Properties
• Density 100% 24.0%
kg/m3 5515 1326
• Jupiter’s density is only 1.3 x water’s density.
A Truly Wicked Magnetic Field
• Jupiter’s magnetic field is the strongest and largest, next to the sun’s.
• It’s so large that it interacts with the Jovian moons (electrically), and even stretches out as far as Saturn.
Field is 14Xstrongerthan earth’sfield at theequator…
4.2 Gaussvs. 0.3Gauss.
How is a strong field compatible with the low density?
• Chemical composition–90% H by volume (75% by mass)–10% He by volume (25% by mass)–<1% of methane (CH4), ammonia (NH3),
and ammonium hydrosulfide (bright colors)
What is the conductor?
• At the high pressures found in Jupiter’s interior, hydrogen gas becomes a liquid metal, and therefore electrically conductive.
• At least 1.4 Megabars of pressure are required.
Metallic Hydrogen
• Metallic hydrogen has been produced in a lab by shock compressing gaseous H.
• Here’s a website from the researchers that first made metallic H if you’d like to read further:
https://www.llnl.gov/str/Nellis.html
Orbit
• Average distance from the sun:
778.6 million km (5.2 A.U.)
• Perihelion: 740.5 million km• Aphelion: 816.6 million km
• Orbit Eccentricity: 0.049
Orbit (2)
• Orbital Period: 11.86 years– Orbital Velocity: 13.1 km/s
• Inclination of orbit to ecliptic: 1.3o
– We have modern evidence that Jupiter’s been the target of collisions with other bodies.
Rotation
• Rotational Period: 9.93 hours– Axis is tilted 3.1o to the orbit.– How was this measured? (3 ways)
• Homework question: A point on earth’s equator rotates with an eastward velocity of about 1670 km/hour (464 m/s). Calculate the eastward velocity of a point on Jupiter’s equator.
Rotation’s Effect on Jupiter’s Weather
• No surface N-S convective cells• Belts (upwelling gas, darker stripes)**• Zones (sinking gas, lighter stripes)**
– Gas flow is in opposite directions• Differential rotation
– Faster at equator (9h 50m)– Slower at poles (9h 56m)
**new result from Cassini spacecraft
Unanswered Questions
• Turbulence and atmospheric friction should have bled off much of Jupiter’s rotational energy, by converting it to kinetic energy in the atmosphere and raising the atmosphere’s temperature.
• Yet Jupiter still rotates very quickly, and the upper atmosphere is cold. Why?
More Rotational Effects
• Great Red Spot– first observed in 1664 by Robert Hooke– size, color, shape changes regularly– predatory!
• Great Red Spot Junior• White Ovals
Great Red Spot moviehttp://antwrp.gsfc.nasa.gov/apod/ap001123.html
All the Gas Giants have rings!
• Jupiter has a set of 4 rings–much less substantial than Saturn’s
rings–only visible by backlighting–Discovered by Voyager 1–Formed from dust blasted off 4 small
inner moons by impacts (Amalthea, Andrastea, Metis, Thebe)
The backlit rings are totally inside Io’s orbit.
