Friday April 16th 1999
Announcements:

Lecture notes:

Class 41.
Jupiter.

Can learn mass from how the moons orbit - use laws of gravity
Very massive = about 317 Earth masses.

Over 2X mass of all other planets combined.  But still 1000 times less than Sun.
Sun and Jupiter - all else is debris.
Get radius from angular size (71000 km).  Then solve for density. 1300 kg/m³ much less terrestrial planet.

Tells you not rocks - gas giant.
86% H by mass
14% He by mass.  trace other things.

Rotation.
Can watch features move.  See differential rotation - not like Earth.  Equator is faster ( 9h 50m) higher latitudes are 9h 56m.
Can do this because it is fluid.  Sun also rotates this way.  15M Earth core of Jupiter rotates like a solid body every 9h 56m.
Know this from measurements in radio.  Since magnetic field is frozen into core.
Bulges at the equator by 6.5% due to rotation.

Climate and atmosphere.
Tilt of Jupiter's equator from orbital plane only 3 degrees.  No seasons.

Has cloud layers - complicated chemistry and turbulent motions.  Total thickness is 80 km.  Colors are due to holes in upper
atmosphere.

Atmospheric.  Bright zones - above upward moving currents.  Dark belts - material is sinking like storm systems on Earth but
stretched all the way around Jupiter due to rapid rotation.

Great Red Spot
Giant cyclone 4x radius of Earth.  Has lived for > 300 years. Rotates counterclockwise each 6 days.  Why red?  not well known but complex chemical reactions are involved.

Internal Heating.
Jupiter emits 2x as much heat as it receives from the Sun.  Still radiating heat from gravitational collapse since heat is trapped in by atmosphere.

Magnetosphere.
Magnetic field over 10x as strong as Earth's Jupiter surrounded by charged particles that move along B field lines.

Sort of like Earth's aurorae but far more intense.  Because of this we need to shield spacecraft going to Jupiter.  Magnetic
"sphere of influence" sticks out past Saturn.

Ring
<30 km thick and goes out to 1.81 planetary radii.
<100 times less opaque than Saturn's ring and probably made of dark red silicate materials.
Most particles are tiny - dust specks.
Thought to be made when micrometeorites strike moons Adrastea and Metis
 
 

Name	Distance from Sun	Mass	Radius	Density
Jupiter	5.2 AU	317 M Earth	10.9 R Earth	1333 kg/m3
Saturn	9.5	95	9.2	680
Uranus	19.19	14	4.0	1200
Neptune	30.1	17	3.9	1600

Earth's mass = 6x10 ²⁴Kg
Earth's radius = 6370 km
Earth's density = 5517 kg/m³