Saturn

Astronomy 311Professor Lee

CarknerLecture 18

Which of the following is a major component of Jupiter’s clouds?

a) Waterb) Ammonia c) Molecular hydrogen d) a and b onlye) a, b, and c

In what region does Jupiter generate its strong magnetic field?a) Rock/ice coreb) Liquid metallic hydrogen

mantlec) Molecular hydrogen atmosphered) Dust ringe) Alternating cloud bands

Saturn -- King of the Titans

He was overthrown by Jupiter who became king of the gods

Saturn’s symbol is the sickle

Viewing Saturn from Earth

First viewed through a telescope by Galileo

Modern telescopes reveal a series of rings and cloud patterns in Saturn’s atmosphere

Saturn Facts

Size: 9.5 Earth diameters

Orbit: 9.5 AU

Description: smaller, more distant Jupiter with rings

Viewing Saturn from Space

Hubble Space Telescope has provided many images

Orbiting Saturn to study it long term Dropped a probe (Huygens) into Titan’s

atmosphere

Path of Cassini

Saturn’s Atmosphere

Saturn has belts, zones, ovals and storms, but they are less distinct than on Jupiter

Colors tend to be yellow, white and brown

Saturn sometimes has storms that burst up from below

Composition of Atmosphere

Top layer of Ammonia (NH3) Middle layer of Ammonium Hydrosulfide

(NH4SH)

We don’t see all of the layers as clearly as we do on Jupiter

Saturn’s Dullness The temperature of Saturn’s atmosphere

increases more slowly with depth than Jupiter because:

Due to weaker gravity the layers are more spread out

As a result Upper layers obscure the deeper layers

Saturn and Jupiter’s Atmospheric Structure

Saturn’s Heat

Saturn is smaller than Jupiter and should have radiated much of its heat away by now

Theory: the helium condensed into droplets and fell towards the core liberating gravitational energy Calculations seem to support this

Saturn’s Interior Saturn is also the most oblate planet

The density is low due to a much smaller liquid metallic hydrogen mantle

Saturn has a magnetosphere but it is not as strong as Jupiter’s Due to slower rotation, less liquid hydrogen and blocking of

charged particles by the rings

Internal Structure of Jupiter

and Saturn

HST Views the Rings Edge-On

Rings and Tides

This is the region where the tidal force pulling the material apart is stronger than the gravitational force holding it together

3Roche ρ

4MR

Structure of the Rings

Rings are separated by gaps or divisions with relatively few particles

The size and composition of particles vary from ring to ring F ring has many small, dark particles

Diagram of Saturn’s Rings

Moons and the Rings Several moons have orbits within the rings

Moons may also be a source of ring material Examples of moons effecting the rings:

The Encke gap has a small moon, Pan, in it

Next Time

Read Chapter 13.1-13.6

Summary Saturn is the second largest planet and

the second closest gas giant to Earth Saturn is similar to Jupiter with key

exceptions mostly due to less mass and smaller gravity cloud layers are more spread out in depth less distinct cloud bands larger core less liquid metallic hydrogen

Summary: Rings

Made up of many distinct rings and ringlets

Composed mostly of icy particles of various sizes and reflectivity

Ring structure shaped by moons Rings cannot form a larger body

due to tidal forces