The Saturn

In our universe there are nine, us known, planets:

Saturn is the sixth planet from the sun and the second largest.

Mercury, Venus, Earth, Mars, Jupiter, Saturn , Uranus, Neptum, Pluto

Saturn was the god of agriculture, he was called Cronus by the Greeks. He is the son of Uranus, and father of Jupiter (Zeus). Saturn over threw his father to become king of the gods, but was then over thrown himself by his son Jupiter.

Saturn is the root of the English word "Saturday"

Saturn is a favourite object for many observers. It's beautiful rings are 169,800 miles wide, but less thick than a football field. In many ways Saturn is similar to Jupiter, but it is much smaller. Under the clouds of methane and helium the sky gradually turns into liquid until it becomes a giant ocean of liquid chemicals.

Saturn is probably the best known, and most beautiful planet in the Solar System. While its possession of a ring system it not unique, it has a set of rings which are far more extensive and more easily seen than any other planet. It is this ring system that makes Saturn so beautiful.

However it is not the only planet with rings. Jupiter, Uranus, and Neptune also have rings.

Planet Profile

Mass (kg)                               ................……….…..….        5.69 x 10^26

Diameter (km)                       ...................……….……        120660

Mean density (kg/m^3)         ......................……..……       .690

Escape velocity (m/sec)      ........................………...         35600

Average distance from Sun (AU)....................……..          9.539

Rotation period (length of day in Earth hours).....….         10.2

Revolution period (length of year in Earth years)..…         29.46

Obliquity (tilt of axis in degrees)...............…………..         26.7

Orbit inclination (degrees)........................…………..         2.49

Orbit eccentricity (deviation from circular).......……..         0.056

Mean temperature (K)..............................…………..          88 K (1 bar level)

Visual geometric albedo(reflectivity)..........………...         0.46

Atmospheric components.............................……….          97% hydrogen, 3% helium, 05% methane

Rings............................................…………………...           Rings are 270,000 km in diameter, but only a few hundred meters thick. Particles are centimeters to decameters in size and are ice (some may be covered with ice); there are traces of silicate and carbon minerals. There are four main ring groups and three more faint, narrow ring groups separated by gaps called divisions.

Because Saturn is bigger than the Earth, you would weigh more on Saturn than you do here. If you weigh 70 pounds on Earth you would weigh 82 pounds on Saturn.

The Planetary Interior








Like Jupiter, Saturn is composed mainly of the light elements hydrogen and helium. At its centre there is believed to be a core of rocky material about the size of the Earth, but more dense. Around this is a metallic hydrogen shell some 30,000 kms deep. Above this is a region composed of liquid hydrogen and helium with a gaseous atmosphere some 1,000 kms deep in which are the cloud structures that look like the surface of the planet.

The Atmosphere

Saturn is composed of about 94 percent hydrogen and 6 percent helium. The clouds are composed of very small amounts of other chemical elements combined with hydrogen to give such compounds as ammonia, methane and phosphine. Because Saturn is colder than Jupiter the more colourful chemicals occur lower in its atmosphere and are not seen; this results in much less dramatic markings but they are similar to those seen on Jupiter, taking the form of bands with some smallish spots.

The Rings

Saturn's rings were first seen by Galileo but were identified as a ring system by Huygens in 1656. For many years Saturn was thought to be unique in having a ring system but we know now that all the major gaseous-planets have ring systems although none is so prominent as that of Saturn.

The rings are divided up into several distinct rings with gaps between them. The largest gap was discovered by Cassini in 1675 but we now know that there is a very complex structure to the ring system.

The rings are composed of many, many small particles up to about 10 metres across. These are thought to have originated in a satellite which collided with a minor planet and/or that they are made of matter which was present when the planets were formed. Saturn's rings are very reflective and could be composed of ices such as make up comets.

                   Radius   Radius             approx.   approx.  
   Name               inner    outer     width  position  mass (kg) 
----              ------   ------     -----  --------  -------- 
D-Ring            67,000   74,500     7,500    (ring) 
Guerin Division   
C-Ring            74,500   92,000    17,500    (ring)  1.1e18 
Maxwell Division  87,500   88,000       500  (divide) 
B-Ring            92,000  117,500    25,500    (ring)  2.8e19 
Cassini Division 115,800  120,600     4,800  (divide) 
Huygens Gap      117,680    (n/a)   285-440  (subdiv) 
A-Ring           122,200  136,800    14,600    (ring)  6.2e18 
Encke Minima     126,430  129,940     3,500   29%-53% 
Encke Division   133,580                325       78% 
F-Ring           140,210             30-500   (ring) 
G-Ring           165,800  173,800     8,000    (ring)  1e7? 
E-Ring           180,000  480,000   300,000    (ring) 
    
 Notes:  
   * distance is kilometers from Saturn's center 
   * the "Encke Minima" is a slang term used by amateur astronomers, not an official IAU designation 

Satellites

With 30 companions, Saturn has more moons than any other planet. Saturn has 8 satellites with diameters greater than 200 kms:

Titan is, by far, the largest; with a dimeter of 5,150 km it is the second largest satellite in the solar system. It is probably the only satellite which has an atmosphere; this atmosphere is denser than the Earth's but is composed almost entirely of methane. Discovered in 1655 by Huygens.

#

RADIUS (km)

MASS (kg)

DISTANCD (km)

DISCOVERER

DATE

VI

2,575

1.35e+23

1,221,850

C. Huygens

1655

Mimas has a diameter of 390 km. Its surface is very cratered and the Voyager pictures show one giant crater with a diameter almost equal to one third of that of the satellite. It   reveals a striking resemblance to the film Star Wars Death Star, therefore it is nick named “The Death-Star” by astronomers. Mima  is named after one of the titans slain by Hercules.

#

RADIUS (km)

MASS (kg)

DISTANCD (km)

DISCOVERER

DATE

I

196

3.80e+19

185,520

W. Herschel

1789

Enceladus has a diameter of 500 km. It shows cratering and also complex geological structures indicating large crustal movements and is the brightest object besides the sun in the solar system. The smooth Surface of Enceladus means that it has recently been active.

#

RADIUS (km)

MASS (kg)

DISTANCD (km)

DISCOVERER

DATE

II

250

8.40e+19

238,020

W. Herschel

1789

Tethys has a diameter of 1,050 km. It appears to be made of ice and is heavily cratered. There is a huge trench-like structure extending a quarter of the way around the satellite which is 100 km wide and 4 to 5 km deep.  In Greek mythology Tethys was a Titaness and sea goddess who was both sister and wife of Oceanus.

#

RADIUS (km)

MASS (kg)

DISTANCD (km)

DISCOVERER

DATE

III

530

7.55e+20

294,660

G. Cassini

1684

Dione is 1,120 km in diameter. It shows many craters and large plains. It is the densest, or heaviest of Saturn's moons.  Dione is named after the Mother of Venus in the Greek Mythology

#

RADIUS (km)

MASS (kg)

DISTANCD (km)

DISCOVERER

DATE

IV

560

1.05e+21

377,400

G. Cassini

1684

Rhea has a diameter of 1,530 km and so it’s the second largest of Saturns moons. Rhea was the Wife of Saturn and mother of Neptune, Jupiter and Pluto.

#

RADIUS (km)

MASS (kg)

DISTANCD (km)

DISCOVERER

DATE

V

765

2.49e+21

527,040

G. Cassini

1672

There are several small satellites some of which are believed to be responsible for `shepherding' some of the features seen in the structure of the rings.

Pan is the closest  moon to saturns surface.  There is not much we know about Pan, because it’s so small and far away. This moon was named after the god of woods, fields, and flocks.

#

RADIUS (km)

MASS (kg)

DISTANCD (km)

DISCOVERER

DATE

XVIII

9.655

?

133,583

M. Showalter

1990

Atlas was a Titan condemned to hold the sky on his shoulders for all eternity. I t orbits Saturn just to the side of the A Ring.

#

RADIUS (km)

MASS (kg)

DISTANCD (km)

DISCOVERER

DATE

XV

20x15

?

137,640

R. Terrile

1980

Prometheus is the inner shepherd satellite of Saturn's F ring. It’s named by a titan who stole the fire from Olymp and gave it to humankind.

#

RADIUS (km)

MASS (kg)

DISTANCD (km)

DISCOVERER

DATE

XVI

72.5x42.5x32.5

2.7e+17

139,350

S. Collins

1980

Pandora outer shepherd moon of the F Ring is named after the first woman, created by Hephaestus endowed by the gods with all the graces and treacherously presented to Epimetheus along with a box  in which Prometheus had confined all the evils that could trouble humanity.

#

RADIUS (km)

MASS (kg)

DISTANCD (km)

DISCOVERER

DATE

XVII

57x42x31

2.2e+17

141,700

S. Collins

1980

Epimetheus is the fith moon of saturns surface. In 1966  it was confused with Janus, another of Saturn's moons they actually trade places with each other every 4 years.  In Greek Mythology Epimetheus was the husband of Pandora.

#

RADIUS (km)

MASS (kg)

DISTANCD (km)

DISCOVERER

DATE

XI

72x54x49

5.6e+17

151,422

R. Walker

1966

Janus is named by the god of gates and doors. Janus is also the root of the name January.  

#

RADIUS (km)

MASS (kg)

DISTANCD (km)

DISCOVERER

DATE

X

98x96x75

2.01e+18

151,472

A. Dollfus

1966

Telesto is one of the smallest moons in the Solar System .

#

RADIUS (km)

MASS (kg)

DISTANCD (km)

DISCOVERER

DATE

XIII

17x14x13

?

294,660

B. Smith

1980

Calypso is one of the smallest moons like Telesto. It’s named after a sea nymph who detained Odysseus on the island of Ogygia for seven years

.

#

RADIUS (km)

MASS (kg)

DISTANCD (km)

DISCOVERER

DATE

XIV

17x11x11

?

294,660

B. Smith

1980

Helene was an Amazon who fought with Achilles, in Greek Mythology. There is not much known about this moon.

#

RADIUS (km)

MASS (kg)

DISTANCD (km)

DISCOVERER

DATE

XII

18x16x15

?

377,400

Laques-Lecacheux

1980

Hyperion   is the largest object in the Solar System that is not ball shaped.  It's probably a  part of a larger rounder moon, which somehow broke apart.

#

RADIUS (km)

MASS (kg)

DISTANCD (km)

DISCOVERER

DATE

VII

205x130x110

1.77e+19

1,481,000

W. Bond

1848

Iapetus is another world made up almost entirely of water ice. It orbits Saturn from top to bottom, not on the equator like most of the other moons.

#

RADIUS (km)

MASS (kg)

DISTANCD (km)

DISCOVERER

DATE

VIII

730

1.88e+21

3,561,300

G. Cassini

1671

Phoebe is much darker than most of the other moons of saturn. It orbits saturn from top to bottom like Iapetus.

#

RADIUS (km)

MASS (kg)

DISTANCD (km)

DISCOVERER

DATE

IX

110

4.0e+18

12,952,000

W. Pickering

1898

S/2000 S 1, S/2000 S 2, S/2000 S 3, S/2000 S 4, S/2000 S 5, S/2000 S 6, S/2000 S 7, S/2000 S 8, S/2000 S 9, S/2000 S 10, S/2000 S 11, and S/2000 S 12.

Appearance

Saturn can easily be seen with the naked-eye. The rings can be seen with a small telescope which will also show the largest satellite, Titan. The Earth passes through the planet every 15 years. The rings are then seen edge-on edge allthough their shadow onto the disk of Saturn may still be visible.

On 1997 October 15 NASA launched the Cassini/Huygens mission which will reach saturn in 2004. Produced by the Information Services Department of the Royal Greenwich Observatory.

Results from the Hubble Space Telescope (HST)

HST has allowed astronomers to obtain images of Saturn which are very high detailed.

In 1997 HST observed the auroral displays on Saturn. These are caused by the interaction between the solar wind and Saturn’s magnetic field and are similar to the displays of ‘northern lights’ seen on Earth although on a much larger scale. However Saturn’s aurora can only be seen in ultraviolet light, which is invisible from the Earth’s surface but clearly visible from HST. The Hubble images reveal ripples and patterns that evolve slowly independently of the rotation of the planet.

Saturn's Aurorae
This image shows  the ultraviolet aurora of saturn, taken by the Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope in October 1997, when Saturn was a distance of 810 million miles  from Earth.
(Image credit: J. Trauger, Jet Propulsion Laboratory and NASA.)

HST also provided images of a rare storm on the surface of Saturn, which measured 7,900 miles across, equal to the diameter of the Earth.

A Storm on Saturn

Here you can see a rare storm that appears as a white arrowhead-shaped feature near the planets equator, which is generated by an upwelling of warmer air, similar to a terrestrial thunderhead.   Picture by  NASA Hubble Space Telescope.
(Image credit: Reta Beebe (New Mexico State University), D. Gilmore, L. Bergeron (STScI), and NASA.)