Saturn














Saturn is the outermost planet of the planets known in ancient times. The earliest known observations of Saturn, by the Babylonians, can be reliably dated to the mid-7th century BC, but it was probably noticed much earlier, since Saturn tends to shine brighter than most stars. To the naked eye it appears yellowish. The Greeks named it after Cronus, the original ruler of Olympus, who in Roman is the god Saturn.
Saturn is the 6th planet in order distance from the sun. It cannot approach the planet Earth closer than 1,190,000,000 kilometers. Its brightness is due to its large size. Saturn’s equatorial diameter is 120,660 kilometers, but its globe is kind of flattened, and the polar diameter is only 108,000 kilometers. The mass of Saturn is 95.17 times that of the Earth, and the escape velocity, which is the velocity which once attained it will enable the object to “coast” away from the planet, is 32.26 kilometers per second, more than three times that of the Earth. Saturn’s outer layers are made up of gas, it is a world quite unlike our own.
Saturn’s ring system is in a class of its own. While Jupiter and Uranus also have rings, those of Saturn are striking, and a telescope of moderate power will show them excellently. There can be no doubt that Saturn is one of the most beautiful objects in the sky.



The first telescopic observations of Saturn have been made by Galileo in July 1610. He saw the disk of the planet clearly, but his telescope gave only a magnification of 32 diameters and that was not good enough to show the ring system in the way we know it nowadays. Galileo thought that Saturn must be a triple planet and wrote that “Saturn is not one alone, but is composed of three, which almost touch one another.” Two years later, he found to his surprise that the “companions” had vanished, so that Saturn appeared as a single object. The ring system was then edge-on to the Earth, and this is why it could not be seen in Galileo’s telescope. The original aspect was seen again in the years following 1613, but Galileo was never able to interpret it correctly. Various strange theories were proposed to explain the planet’s unusual form. Hevelius of Danzig, for example, believed Saturn to be elliptical in shape, with two “appendages” attached to the surface.
The problem was solved by a Dutch astronomer, Christian Huygens, who began his observations in 1655. The telescopes that he used were much more powerful than Galileo’s, and gave a sharper defintion, so in a short time he concluded that “ Saturn is surrounded by a thin, flat ring which nowhere touches the body of the planet.” His theory was not widely excepted, but by 1665 it had been universally accepted, even though the nature of the ring system was not established until much later. Data for Saturn are given in table one on the next page.

Table 1: Planetary Data For Saturn
Distance from the Sun Mean 9.54 a.u. (1,472,000,000 km)
Maximum 10.07 a.u.
Minimum 9.01 a.u.
Sidereal period of revolution 10,759.20 days, or 29.26 years
Mean synodic period 378.1 days
Rotation period(means) 10 hours 39 minutes 24 seconds
Mean orbital velocity 9.6 km/sec.
Axial inclination 26 44’
Orbital inclination to the elliptic 2 29’22”
Orbital eccentricity 0.056
Diameter (equatorial)
(polar) 120,660 km
108,000 km
Apparent diameter seen from Earth Maximum 21”
Minimum 15”
Mass (Earth=1) 95.17
Volume (Earth=1) 744
Density (water=1) 0.7
Albedo 0.61
Satellites 15











Among planetary orbits, that of Saturn is of fairly low eccentricity (0.056), though the difference in distance between perihelion (closest approach to the Sun) and aphelion (farthest retreat from the Sun) amounts to 160,000,000 kilometers. Because Saturn is so far from the Sun and the Earth Saturn always appears to be full, or nearly so, in the sense of the full moon.
The mean synodic period, the interval between successive oppositions, when the Earth passes approximately between Saturn and the Sun, is 378.1 days, so that Saturn is well placed for observation during several months in each year. Opposition dates up to 1990 are April 8, 1982; April 21, 1983; May 3, 1984; May 15, 1985; May 27, 1986; June 9, 1987; June 20, 1988; July 2, 1989; and July 14, 1990.
Like all the superior planets, that is all outwards from the Earth, Saturn moves for the greater part of each year eastward. Its average rate is about 1 in eight days. As