THE PLANET SATURN.

New Zealand Herald, Volume XXIX, Issue 8842, 2 April 1892, Page 1 (Supplement)

THE PLANET SATURN.

The planet Saturn may now bo seen in the eastern sky after sunset. Tho brightest stars in the same quarter of the heavens are Regulua and Spica. They are nearly in a lino with, and equidistant from, the planet, the former to the left and higher, lie latter to the right, and lower. On a clear night a careful observer with good sight may notice the difference in the appearance of the planet and tho stars, the former shining with a steady light, the latter scintillating. If the eye be aided by a telescope, even of small size, this distinction will bo moro evident. The planet will appear larger, while the stars will only sparkle more brilliantly ; and if a powerful telescope be used the form of the planet will be defined, while the stars will remain but. points of light, though of wonderful brilliance. On March 17 Saturn was in opposition to the ■sun, attaining its greatest altitude at midnight. Rising earlier each night, it will culminate at 11 p.m. at the beginning of April, and at 9 p.m. at the end of that month. It is therefore in the position most convenient for observation.

Before the invention of tho telescope Saturn presented no peculiarity to the view of man other than its very slow motion among the stars, \ years being occupied in traversing its path round to the same place ag.-iin. In 1610 Galileo, having succeeded in his efforts to mako a telescope, though bur a poor on" con-inured with

sari. n->. modern instruments, was surprised to find Saturn had an appendage on either side like a small orb. and made the following record : — " i have discovered that the most distant planet is triple" (tergeminum). During successive years he noted changes which puzzled him. Halt a century later Huvgens, with improved instruments, defined the planet as surrounded by a ring and attended by a satellite. He seemed to think nothing further could be discovered, for he said, "The solar system is now complete. It consists of six planets and six moons." Since that period this remarkable orb has been examined with care and assiduity by many observers, and it is now known to be surrounded by several concentric rings, very thin, but extensive, and by eight moons. Depending on the sun for its il lumination, portions of the globe are in shadow where the rings have intercepted the light, and it in turn casts its shadow on the opposite part of the rings. As the direction of the planet's axis remains unchanged during its orbit round the sun, each portion of the rings' circumference is successively turned toward that luminary, therefore the position and form of the shadow is always changing.

No wonder then that those who see these things are struck with amazement and awe. .Sir K. Ball, the Astronomer Royal for ireland, refers to the " Marvellous system of Saturn'' as being ''wonderful from every point of view, and so far as o lr knowledge goes without a parallel in the wide extent of the universe." The late Mr. Proctor remarked, " I can well remember the sensation with which 1 looked on the ringed planet for the first time. 1 look on that view as my introduction to the most fascinating of all the sciences." It is unfortunate, however, that the details of a view so interesting require for their examination the aid of an instrument of considerable power, and such an instrument. is useless unless firmly and substantially mounted, hence tew persons have the opportunity of gazing on it,- glories. Some conception of the phases of the ring may be formed by means of a model made as follows : In the centre of a ring of card whose inner and outer diameters are respectively three and a quarter inches and live inches,

orbit; which produce some singular phenomena when Saturn is traversing those two opposite parts of its orbit where the ring appears to close. During the greater part of last year the ring wis approaching this phase. In September the line of si<rlit from the earth became coincident with the place a two-inch ball, attaching the same by wires ; put the ball on a little block (two pennies will do) and incline the ring so that one edge will rest on the table ; then insert a wire in the ball vertically. If the model be then placed at the height, of the eye and viewed at a distance of several yards while a fiiend rotates it on its vertical axis once, the perspective of the ring will vary between an ellipse and a fine lino twice. Just so Saturn's ring appears to open out and close up twice during its long extended journey round the sun. There are some minor fluctuations caused by the varying positions of the earth in its plane of the ring, and then crossing it, the ring disappeared for live weeks until the sun also crossed it, and the earth and sun being again on the same side the ring reap peared and opened out slightly till the earth reached its summer limit at the end of the year, the ring then began to reclose and now appears as a line. On or about May 21 the line will have become so thin as to be invisible without the aid of a powerful instrument, after which it will open out again. In the spring Saturn was in an unfavourable position tor observation, but as now it is otherwise, all available telescopes will be turned upon it, as a similar opportunity will not present itself for fifteen years. On such occasions the inner satellites of Saturn have been seen like beads threaded on the fine streak of light, and astronomers look forward to them with great interest, not perhaps without some pardonable hope of making fresh discoveries. But if this phase be so beautiful what shall wo say of that sceno presented when the ring is opened out and the moons appear scattered around ? Then again we use the full power of mir be«t instruments,

SATURN. — KING OI'KNED OUT TO FULLEST EXTENT AS SEEN FROM EARTH. and strain the eye to scrutinize all the markings and the smallest differences of shading to ascertain all we can of the structure, and changes, if any, that may be going on. The ring is seen to be divided into several zones more or less separated ; the innermost, being much less dense than the others, is commonly called the " crape ring." From time to time measurements have been made, and it has thereby been ascertained that the zones and spaces change in width and density. This helps us to judge of the nature of this singular appendage, the most generally received opinion being that it consists of innumerable shoals of minute satellites rapidly revolving. The diameter of Saturn is estimated as being more than nine times that of the earth, and its volume 700 times. This mighty globe circling round the sun at the inconceivable distance of 900,000,000 mile:', or ten times the distance of our world, revolves on its axis in ten and a-half hours only 1 Vast as is its distance, it is not, as Galileo and Huygens thought, the boundary of the solar system, for wo know of other planets and satellites so much further plunged into the depths of spaco that they

are invisible to the naked eye, and require more time to swoep once round their central ruler than is allotted to any individual man to observe them. John KIGG. Observatory, Thames, March, 1892,