STARLIGHT

Press, Volume LXXIII, Issue 22121, 17 June 1937, Page 6 (Supplement)

STARLIGHT

(By B. W. Collins)

The second of the outer group of the sun's family of planets is seen through a telescope to be a most peculiar object Even to the naked ,ye it has much of ft at the extreme outer limit of tne solar system as known to the ancient astronomers, and they thought it was the matjjrtart bodyin the heavens apart from the fixed stars. There are three planets further away even than Saturn, but they can be seen only in a telesec?*.'The slow and stately movement of this planet suggested great age and.vast experience, and so it was named after the Roman god Saturn who was said to have been king of the world to the {"-off days before men existed This god was also very cruel and bad-tem-pered, and even to-day we speak of a gloomy, depressed person as "saturnine." . „ Saturn is more than nine and a half times as far from the sun as the earth. Its average distance is

888,000,000 miles, but the actual distance varies by 50,000,000 miles as the planet's orbit is not a perfect circle but an ellipse. ■ Since the earth also revolves round the sun in a smaller orbit than Saturn and at a different speed, the distance between the two planets varies «reatly. When both are on the «ame side of the sun it may be as little as 744,000,000 miles, and when they are on opposite sides it may be as great as 1,028,000,000 miles, : This variation in distance causes the size of* the disc of Saturn as ■een through a telescope to change •lao, and so the most favourable

SATURN, THE RINGED PLANET

time for astronomers to study the planet is when both the earth and Saturn are on the same side of the sun, and the apparent diameter is largest.

The path in which Saturn moves round the sun is nearly 10 times as long as that of the earth, and its speed is less than a third as fast. It rushes along at six miles a second instead of 18J as we are doing at this moment on the earth. It, therefore, takes a much longer tune to Fo round the sun, its "year" being equal to 29* of our earthly years. In size the planet holds second place in the solar system. It Is Jupiter's next younger brother, our earth being only the fifth member of the family. Its volume is more than 760 times that of the earth, or about half as big as Jupiter. For its large size its weight is small, being only 95 times that of the earth. In consequence, the average density of Saturn is very lowonly two-thirds that of water, whereas the average density of the earth is five and a half times that of water. Saturn is thus formed of lighter material than any other planet. This member of the sun's family is unique in yet another respect. It is the most flattened. Air the planets are slightly distorted from the perfect spherical shape, becoming what are known as oblate spheroids. This is due to their rotation or spinning. Saturn, owing to its low density and high rate of rotation, is more distorted than any other 'planet, the compress on at each pole being greater than the radius of the earth $»« » w swat that it may readily be detected in the view of the planet ma telescope or in a vhaltomvh. mean diameter is nine times that of the earth, but the equatorial diameter is 75,100 miles and the polar SWMO. The large difTerence-7900 m les—is due, as mentioned above, KhVrapid rotation of the planet Although nearly 800. times the size of the earth it spins more than twice as fast. The day on Saturn isonly 10 hours 14 minutes. .This is at the equator; for, like £upitex, Saturn is* not as solid as the .earth, and spins more slowly towards the poles. The length of the day in the "temperate zones" is 1C -hours 37 minutes. The axis, is tilted over at an angle of 27 degrees, which, though only four degrees more than the* earth, is more than any other planet except Uranus, its next-door neighbour-, on the outside. Owing to its greater distance from the sun Saturn is even colder than Jupiter. Its composition seems to be very much the same as its elder brother, however, except that it has a much deeper atmosphere. Inside is a solid core of rock about 28,000 miles in diameter, or three and a half times the diameter of the earth. Covering(this Is an enormous layer of ice about

6000 miles thick. Then above this again the atmosphere, consisting mainly of ammonia and marsh gas extends for 16,000 miles. The total weight of this atmosphere is about equal to that of the rocky core. The depth of the atmosphere of Jupiter is only about one-seventh of the whole radius of the planet, whereas on Saturn the atmosphere extends down to a depth equal to about half the total radius. It is because the atmosphere of Saturn is much greater in proportion to its size than on any other planet that the "average density is so low. For the sake of comparison it may -be mentioned that the thickness of the earth's atmosphere is only approximately one-fortieth of its radius. The markings seen on of Saturn are thought to be belts of clouds in its atmosphere, and they have been carefully observed in order to determine the planets period of rotation. _ As seen in the diagram, Saturn is surrounded by a most curious system of rings, making it one of the most beautiful of all celestial objects when seen through a telescope. In this respect, so far as is known, Saturn ia absolutely unique in the universe. "We shall have to

leave fod another article a description of this interesting feature, and also of his family of nine moons.'