Descriptive Astronomy 101


The sixth planet from the Sun.
Second largest planet in Solar System
Saturn is a gas giant
Large system of rings
Its average density is 0.69 g/cm3


96.3% hydrogen, 3.25% helium
Traces of methane, ammonia, ethane, ethylene, and phosphine.
Saturn is colder than Jupiter
The more colorful chemicals sink lower in its atmosphere and can't seen.
Markings are much less dramatic, although bands and some small spots are still visible.
Alternate jet streams of east-west and west-east circulation
Speeds of up to about 1,800 kph


Core: rocky and metallic (?) - material about the size of the Earth, but more dense.
Ices shell (?)
Metallic hydrogen shell some
Molecular hydrogen and helium
Gaseous atmosphere: hydrogen, methane, ammonia, water

Magnetic Field

Modest magnetic field similar in strength to Earth's.
Auroral displays caused by the interaction between the solar wind and the planetary magnetic field.


The most spectacular ring system and largest ring system in the solar system
Composed of swarms of ice-rock particles ranging in size from a centimeter to several meters across (and possibly even as large as a kilometer),
80,000 km wide band
280,420 km diameter
Only about a kilometer or so thick
Ring matter will orbit a planet without coalescing into a single body if it remains within a certain distance, known as the Roche limit.
Any bodies that orbit outside this limit won't be adversely affected by the gravity of the parent planet and may therefore accrete into a larger body.
Ring Nomenclature.

Roche Limit

The smallest distance that a satellite can orbit from the center of a planet without being torn apart by tidal forces.
The critical distance is 2.44 times the radius of the primary.
The shattering of satellites in orbits well inside the Roche limit may explain the origin of some planetary ring systems.


Saturn has 47 known moons
The three largest:
Iapetus: 1460 km diameter
Rhea: 1530 km diameter
Titan: 5140 km diameter


The largest moon of Saturn and the second largest moon in the Solar System
Only moon in the Solar System to have a dense atmosphere (10 times deeper than Earth's and surface pressure 60% greater).
Composed primarily of nitrogen, with smaller amounts of methane and hydrogen.
Methane traps some solar heat and creating a modest greenhouse effect.
There are no visible craters
Indicates that the surface has recently resurfaced.
Flow patterns on Titan's surface
Caused by??
Volcanic eruptions; shifting plates of rock; wind-blown dust; rivers of liquid hydrocarbons.
Liquid pools on the surface?

Titan - Huygens probe

Successful surface landing on Jan. 14, 2005
Descent and surface pictures.
Reveals apparent drainage channels leading to a dark body of liquid (?)
Flat surface strewn with boulders.

Saturn Facts

Distance from Sun 9.54 AU
Distance from Sun 1,427 million km
Equatorial diameter 120,536 km
Polar diameter 108,728 km
Equatorial diameter (Earth=1) 9.449
Mass (Earth=1) 95.2
Mean density 0.69 g/cm3
Axial period 10.2 hours
Axial inclination 26.7°
Orbital period 29.46 years
Orbital inclination 2.5°
Orbital eccentricity 0.056
Gravity at cloud-tops (Earth=1) 0.92
Escape velocity 35.47 km/s
Albedo 0.61