SATURN
, one of the primary planets, being the 6th in order of distance from the sun, and the outermost of all, except the Georgian planet, or Herschel, lately discovered; and is marked with the character , denoting an old man supporting himself with a staff, representing the ancient god Saturn.
Saturn shines with but a feeble light, partly on account of his great distance, and partly from its dull red colour. This planet is perhaps one of the most engaging objects that astronomy offers to our view; it is surrounded with a double ring, one without the other, and beyond these by 7 Satellites, all in the plane of the rings; the rings and planets being all dark and dense bodies, like Saturn himself, these bodies casting their shadows mutually one upon another; though the reflected light of the rings is usually brighter than that of the planet itself.
Saturn has also certain obscure zones, or belts, appearing at times across his disc, like those of Jupiter, which are changeable, and are probably obscurations in his atmosphere. Dr. Herschel, Philos. Trans. 1790, shews that Saturn has a dense atmosphere; that he revolves about an axis, which is perpendicular to the plane of the rings; that his figure is, like the other planets, the oblate spheroid, being flatted at the poles, the polar diameter being to the equatorial one as 10 to 11; that his ring has a motion of rotation in its own plane, its axis of motion being the same as that of Saturn himself, and its periodical time equal to 10h 32′ 15″.4. See also Ring, and Satellite.
Concerning the discovery of the ring and figure of Saturn; we find that Galileo first perceived that his figure is not round: but Huygens shewed, in his Systema Saturniana 1659, that this was owing to the positions of his ring; for his spheroidical form could only be seen by Herschel's telescope; though indeed Cassini, in an observation made June 19, 1692, saw the oval figure of Saturn's shadow upon his ring.
Mr. Bugge determines (Philos. Trans. 1787, pa. 42) the heliocentric longitude of Saturn's descending node to be 9s 21° 5′ 8″1/2; and that the planet was in that node August 21, 1784, at 18h 20′ 10″, time at Copenhagen.
The annual period of Saturn about the sun, is 10759 days 7 hours, or almost 30 years; and his diameter is about 67000 miles, or near 8 1/2 times the diameter of the earth; also his distance is about 9 1/2 times that of the earth. Hence some have concluded that his light and heat are entirely unfit for rational inhabitants. But that their light is not so weak as we imagine, is evident from their brightness in the night time. Besides, allowing the sun's light to be 45000 times as strong, with respect to us, as the light of the moon when full, the sun will afford 500 times as much light to Saturn as the full moon does to us, and 1600 times as much to Jupiter. So that these two planets, even without any moon, would be much more enlightened than we at first imagine; and by having so many, they may be very comfortable places of residence. Their heat, so far as it depends on the force of the sun's rays, is certainly much less than ours; to which no doubt the bodies of their inhabitants are as well adapted as ours are to the seasons we enjoy. And if it be considered that Jupiter never has any winter, even at his poles, which probably is also the case with Saturn, the cold cannot be so intense on these two planets as is generally imagined. To this may be added, that there may be something in the nature of their mould warmer than in that of our earth; and we find that all our heat does not depend on the rays of the sun; for if it did, we should always have the same months equally hot or cold at their annual return, which is very far from being the case.
See the articles Planet, Period, Ring, SATELLITE.
