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Physics 320: Astronomy and
Astrophysics – Lecture XIII
Carsten Denker
Physics Department
Center for Solar–Terrestrial Research
NJIT
The Jovian
Worlds
 The
Giant Planets
 The Jovian Moons
 Io
 Europa
 Ganymede
 Callisto
 Ring
System
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December 3rd, 2003
The Giant Planets
Jupiter, Saturn, Uranus,
and Neptune = 99.5% of
the entire mass of the
planetary system
 Galileo Galilei 1610 
Galilean moons and
Saturn’s ring (telescope)
 Pioneer 10/11 and
Voyager ½
 Galileo and CassiniHuygens
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Contribution of
degenerate electron
pressure
 Brown dwarfs must
have masses less than
about 80 MJupiter
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Jupiter
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Shoemaker-Levy 9
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Atmosphere
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December 3rd, 2003
Oblateness
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Equatorial radius:
Re = 71,370 km
Polar radius:
Rp = 66,750 km
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Oblateness:
(Re  Rp) / Re = 0.0648
First order correction term in
gravitational potential:   U / m
4
  Re 2
R
 e
1

J
P
cos


J 4 P4  cos   


   2 2


 r 
  r 
GM
( )  
r
P0 (cos  )  1
1
P2 (cos  ) 
3cos 2   1
2
1
P4 (cos  )  34 cos 4   30 cos 2   3
8



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


Legendre Polynomials

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Gravitational Moments
 J2:
oblateness and
moment of inertia
 J4: mass distribution in
outer regions, equatorial
bulge, and planets
thermal structure
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December 3rd, 2003
The Jovian Moons
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Galilean moon: Io,
Europa, Ganymede, and
Callisto
Rock  increase of
water-ice crust (volatiles)
Formation of moons
linked to formation of
Jupiter itself
Hot Jupiter 
evaporation of volatiles
on the closer moons
Tidal interactions 
volcanism
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Volcanism similar to
geysers (sulfur and sulfur
dioxide SO2)
 Resonance in orbits of Io,
Europa, and Ganymede:
1:2:4 ratio of orbital periods
 Galilean moons are located
inside Jupiter’s
magnetosphere (210 times
rJupiter
 vIo = 57 km/s  potential
differences of up to 600 kV
and currents of up to 106 A
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Io
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Magnetosphere
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Volcanism on Io
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Europa
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Ganymede
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Callisto
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Internal Structure
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Saturn
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Ring Systems
Cassini division
 Encke gap
 Thousands of ringlets
 F ring is very narrow
and appears to be
braided
 Ring extend about 5
rSaturn and are very thin
( 10 m, ripples  1 km)
 Optical depth of ring
system between 0.1 and 2
 Partially inelastic
collisions keep rings thin
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Ring particles are small, a
few centimeters to several
meters
Rings are highly reflective
(albedos in the range from
0.2 to 0.6)
Ring systems of Jupiter,
Uranus, and Neptune
Keplerian shear
Shepherd moons
Orbital resonance
Spiral density waves
Poynting-Robertson effect
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Atmosphere
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Uranus
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Seasons on Uranus
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Neptune
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Comparison of Internal Structure
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Homework Class Project
Continue improving the PPT presentation.
 Use the abstract from the previous assignment
as a starting point for a PowerPoint presentation.
 The PPT presentation should have between 5
and 10 slides.
 Bring a print-out of the draft version to the next
class as a discussion template for group work
 Homework is due Wednesday December 10th,
2003. Last chance!

NJIT Center for Solar-Terrestrial Research
December 3rd, 2003