njit physics 320: astronomy and astrophysics – lecture xiii carsten denker physics department...

NJIT

Physics 320: Astronomy and Astrophysics – Lecture XIII

Carsten Denker

Physics DepartmentCenter for Solar–Terrestrial Research

December 3rd, 2003NJIT Center for Solar-Terrestrial Research

The Jovian Worlds

The Giant PlanetsThe Jovian Moons

Io Europa Ganymede Callisto

Ring System


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 Cassini-Huygens

Contribution of degenerate electron pressure

Brown dwarfs must have masses less than about 80 MJupiter


Jupiter


Shoemaker-Levy 9


Atmosphere


Oblateness

Equatorial radius: Re = 71,370 km

Polar radius: Rp = 66,750 km

Oblateness: (Re Rp) / Re = 0.0648

First order correction term in gravitational potential: U / m

2 4

2 2 4 4( ) 1 cos cose eR RGMJ P J P

r r r

0

22

4 24

Legendre Polynomia

(cos ) 1

1(cos ) 3cos 1

21

(cos ) 34cos 30cos 38

ls

P

P

P


Gravitational Moments J2: oblateness and

moment of inertia J4: mass distribution in

outer regions, equatorial bulge, and planets thermal structure


The Jovian Moons

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

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


Io


Magnetosphere


Volcanism on Io


Europa


Ganymede


Callisto


Internal Structure


Saturn


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

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


Atmosphere


Uranus


Seasons on Uranus


Neptune


Comparison of Internal Structure


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 physics 320: astronomy and astrophysics – lecture xiii carsten denker physics department...

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