Jupiter & SaturnLecture 22

Jupiter & Saturn at glance

As seen from the Earth

As seen from the space

Differential RotationDifferential rotation typifies Jupiter and Saturn: Particles at different locations in the fluid take different lengths of time to complete one rotation.

Solid rotation typifies the terrestrial planets: Every part of the object takes exactly the same time to complete one rotation.

(a) Pioneer 11, December 1974 (c) HST, February 1995(b) Voyager 2, July 1979

White ovals

The Great Red Spot lies within a white zone.

A dark belt has encroached on the Great Red Spot.

The Great Red Spot again lies within a white zone.

20,000 km Earth’s diameter

Turbulence downwind of the Great Red Spot

Winds on the north side of the Great Red Spot flow westward.

Winds on the south side of the Great Red Spot flow eastward.

Winds within the Great Red Spot circulate counterclockwise.

Great Red Spot of Jupiter

Regularities in Jupiter’s Atmosphere

http://bcs.whfreeman.com/webpub/astronomy/Videos/MotionsofJupitersAtmosphere_clearSkin_3/MotionsofJupitersAtmosphere.html

Great Red Spot is a strong massive storm

Atmospheres

Saturn has lower atmospheric temperatures than Jupiter.

Saturn has weaker surface gravity than Jupiter, so its cloud layers are more spread out.

Internal Structure

Jupiter’s Magnetic Field

Saturn’s Magnetic Field

Saturn’s Ring

Gravitational effects carve gaps in the rings and focus ring particles into narrow ringlets.

Shaping a ringhttp://bcs.whfreeman.com/webpub/astronomy/Videos/ShapingSaturnsFRing_clearSkin_3/ShapingSaturnsFRing.html

Changing Appearance of Saturn’s Ring

Jupiter has a ring too! Saturn’s ring = icy fragment Jupiter’s ring = rocky particles

Voyager 2 first took an image of “spokes” in the Saturn’s ring. This dark radial features rotate with the Saturn. It is thought to be related to the magnetic field of the Saturn

Cannot be a shape due to the gravitational force alone. Why?

Spokes in the Saturn’s Ring

Roche Limit

Within ~2.5 times the radius of a planet, it’s dangerous!

In summary…

Important ConceptsComposition & StructureAtmosphere and Magnetic FieldsOrigin of rings

Important TermsDifferential RotationRoche limit

Chapter/sections covered in this lecture : Chapter 12