THE PLANETS

Round the year with the stars by Garrett Putman Serviss is part of the HackerNoon Books Series. You can jump to any chapter in this book here. THE PLANETS

THE PLANETS

The beginner will often be troubled in his observations by the presence in some constellation of a brilliant object which outshines all of the stars shown in his charts, and is plainly an interloper among them. He may at once set the stranger down for one of the planets—it may be Jupiter, Saturn, Mars, or Venus, or possibly, if close to the horizon, Mercury. Uranus and Neptune will not disturb his equanimity, for the latter is never, and the former seldom, visible to the naked eye.

Practice will quickly enable him to distinguish a planet from the true stars, both by its greater apparent size and by the quality of its light. The planets do not twinkle as do the stars. This arises from the fact that they present measurable disks which reflect the sunlight, but do not shine with a light of their own. No star shows a real disk, even when viewed with a powerful telescope. The stars are mere points, and the larger and better the telescope the smaller they appear. This is not to say that they do not look brighter in a telescope, for the larger stars are dazzling when viewed with a glass of large aperture;[Pg but they are so distant that the mightiest of telescopes cannot reveal their real surfaces in the form of disks. The apparent disks which they present are due entirely to irradiation, and the higher the power the smaller these spurious disks appear.

Another way in which the beginner may identify a planet is by observing its motion. No planet remains long in the same position with regard to neighboring stars. They all travel, at varying rates, from west to east through the sky. But this motion is not constant, and at times it is reversed. In the cases of Mars, Jupiter, and Saturn the reversal is due to the fact that when they are in opposition to the sun the earth, being nearer the sun than they are, outfoots them in eastward motion, so that they appear for a time to move backward on their orbits. It is like a fast train passing a slow one on a parallel track; to an observer on the fast train the slow one seems to be either standing still or moving backward. But Mercury and Venus, being nearer the sun than the earth is, have at times a backward motion which is real. Let us consider them only when they appear as “evening stars.” From “superior conjunction” (i. e., the point occupied by the planet when it is on the opposite side of the sun from the earth) to “greatest eastern elongation” (greatest apparent distance from the sun in the evening sky) both Mercury and Venus move eastward among the stars; from “greatest eastern elongation” to “inferior conjunction” (i. e., the point occupied by the planet when it is between the earth and the sun) they move westward among the stars, or, in other words, approach the sun.

The motions of Mercury and Venus are comparatively swift, particularly that of the former. Few persons have ever seen Mercury, because of its nearness to the sun. When well seen it is brighter than any first-magnitude star. As an “evening star” it appears in the west immediately after sunset about once every four months (more precisely once every 116 days). It remains within view about twenty days, but can be easily distinguished only for a week or so when it is nearest eastern elongation. Every almanac gives the dates of its appearances.

Venus, being farther from the sun, travels less rapidly. It reappears in the evening sky once in every 584 days, gradually withdrawing from the sun, and growing brighter until it reaches greatest eastern elongation, which may be as much as forty-seven degrees from the sun, after which it approaches the sun, still becoming brighter for several weeks, until at last it is lost in the glare of the sunlight. During its excursions in the evening sky (and the same is true of its morning apparitions), Venus becomes the most brilliant object in the starry heavens, so brilliant, in fact, that many persons can hardly be persuaded that it is not an artificial light, or some extraordinary phenomenon in space. In the telescope it shows (as does Mercury, also) phases like those of the moon, and when it is seen in the form of a narrow crescent it becomes one of the most charming objects imaginable. For more details about Mercury, Venus, and the other planets, the reader may consult Astronomy with the Naked Eye.

Mars, Jupiter, and Saturn are more likely to cause confusion to the beginner by getting “mixed up” with the stars of the constellations he is studying, because they travel all round the sky, and may appear in turn in each of the zodiacal constellations at any hour of the night. The zodiacal constellations are twelve in number—Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricornus, Aquarius, and Pisces—and they lie in succession along the course of the ecliptic.

Mars is not remarkably brilliant except when it is in opposition to the sun, which happens once every 780 days; but some of the oppositions are much more important than the average, because they occur when Mars is relatively near the earth. This planet is always distinguishable by its ruddy color. In case it is mistaken for a star, the error can be corrected by watching it for a few successive nights, when its motion will become clearly apparent. On the average it moves eastward about half a degree per day.

Jupiter, always very conspicuous when in view, outshines even Sirius, though lacking the scintillation characteristic of that great star. Its light has a slightly yellowish tint, and is remarkably steady. Since it requires nearly twelve years to make a revolution round the sky, Jupiter’s motion is not immediately apparent. It remains for a long time in any constellation in which it may be found, travelling eastward, on the average, about 5′ of arc, or one-sixth of the apparent diameter of the moon, per day. In a month it moves about two and a half degrees.

Saturn is yet more deliberate in its movements. Requiring almost thirty years for a revolution, it may remain more than two years in the same constellation, and its real motion will only become evident upon careful observation continued for several weeks.

The best way to recognize the planets with certainty is to look up their positions with the aid of the American Ephemeris and Nautical Almanac, published annually by the Government at Washington. There the right ascensions and declinations of all the planets are given for any time of the year. Having these, you may find on the large-scale charts the approximate place of the planet sought, and, if you choose, indicate its position with a pencil-mark.

The study of the planets, even without telescopic aid, has a charm hardly less potent than that of the stars. Mercury is fascinating because of the difficulty of seeing him in the light of twilight or dawn. The ancients were greatly puzzled by his dodges, and some of them thought that he was a double personality, and gave him two names, one for his morning and the other for his evening apparitions. With the Egyptians he was respectively Set and Horus, and with the Greeks Apollo and Hermes. The same was true of Venus, who was Phosphorus in the morning and Hesperus in the evening.

Venus, after she passes the half-moon phase, becomes so bright that she simply overpowers all stars in her neighborhood. Her splendor seems almost supernatural, and she has frequently been seen at high noon, a point of intense light burning in the blue sky.

Jupiter’s entrance into any constellation immediately alters its familiar aspect, and he becomes its unquestioned leader, and remains such until his slow eastward motion carries him on to reign in another quarter of the firmament. He is never more impressive than when, in consequence of the annual revolution of the heavens, he rises late some night and takes the lingering star-gazer by surprise. Then all the stellar hosts that for hours have held the watcher spellbound cease their incantation in the presence of this great counter-charmer, to whose power they, too, seem to bow. Although Venus at her brightest outshines Jupiter, she lacks a certain majesty which he alone possesses. His light is calm, steady, insistent, commanding. He does not look like a star, but rather a superstar. If he beams at all, it is not the hurried scintillation of the twinkling multitude around him. Rising through a moisture-laden and wind-swept sky, where the stars are like pulsating atoms, shaken apart and scattered in tinsel showers of rainbow sparks, he glows unflickering, recognizing the aerial tumult only by a deepening of color which makes him the more imposing. As he mounts the heights of the sky he gleams ever brighter and ever steadier, and, casting off the tarnish of the horizon, his supereminent light glows with a splendor that is amazing. If you have an eye that can detect one or two of Jupiter’s moons hiding close in his rays, you may boast of your powers of vision, for that feat has been accomplished by very few human beings. Humboldt heard of a German “master tailor” who could do it. There are a few other cases on record. Most persons cannot see them even with the aid of a strong opera-glass. There is a superstition that they can be seen with a looking-glass, but it is only ghostly reflections that are thus perceived—perhaps as real as any other ghosts.

Saturn, although as bright as a first-magnitude star, is somewhat disappointing as a naked-eye object, owing to the relative dulness of its light. Like Jupiter, it shines with great steadiness, and a practised eye could not mistake it for a fixed star. But its appearance without a telescope gives no hint of the unearthly beauty with which it astonishes the beholder when its rings are rendered visible. Not to have seen those rings at least once in a lifetime, as they appear in a powerful telescope, is to have missed one of the supreme spectacles of creation.

Mars is never very brilliant except during favorable oppositions, when, approaching within less than 40,000,000 miles of the earth, it hangs in the midnight sky, gleaming red like a portent of disaster. The aspect of Mars at such times is truly alarming. It is surprising to see what a quantity of stained sunlight a world only about four thousand miles in diameter is able to reflect across so vast a gap of space. The reason why the ancients connected Mars with the god of war is plain enough when he puts on his color.

Close conjunctions of the bright planets are exceedingly interesting phenomena. Mars and Jupiter seen together when the former is near one of its favorable oppositions make a scene of strange beauty. After long intervals of time several of these great planets sometimes assemble in the same quarter, and such conjunctions are always memorable occurrences. The stars are forgotten in the presence of this new constellation, and yet the tiniest of the sparks that seems to hide its light in the depths beyond would master these great planets and make gravitational slaves of them, as the sun does.

The planets are so conspicuous to our eyes, because of their relative nearness, that it is not easy for the beginner in such studies to realize how insignificant they actually are. But suppose that one could fly like a spirit away from the earth and the neighborhood of the sun, out into the deeps of interstellar space. As he moved away the planets would seem to be swallowed up, one after the other, in the solar rays. First Mercury would disappear, as if it had fallen into the sun. It would be just like two neighboring lights which appear to draw together and blend into one as the observer travels away from them, the greater swallowing the less. Then brilliant Venus would go, plunging into the great solar furnace, to be seen no more. Next the earth would follow in the perspective holocaust. Mars would seem to draw nearer until he, too, disappeared; Jupiter would follow; then Saturn; then Uranus, and finally Neptune. When the last planet was gone the sun would be seen shining alone, unattended, as if he had never had any planets. Thus it may be with the stars; most of them may have systems of planets circling round them, but at our distance these planets are concealed in the rays of their primaries.

One would not need to go so far away as the stars in order to see the sun apparently swallow his planets, as Saturn was fabled to have swallowed his children. But as one approached the stellar region, the sun itself would become a mere star. Fainter and fainter it appears, glimmering and twinkling, deprived of its dominance, stripped of its splendor, a pitiful spark now instead of an all-ruling and blinding maker of daylight, until at last the far voyager from the earth, gazing with his soul in his eyes, straining his vision to the utmost to hold that glinting point clear of its fellows, for it is his sun, suddenly, as a momentary film blurs his sight, loses it, and henceforth seek as he may among the countless hosts that spangle the firmament, he will never again find the day-star under whose cheery beams he was born! Hidden in the Milky Way, one would have no more chance of recognizing the sun than of finding a particular grain of sand on the sea-shore. Man physical is as insignificant as the rock he dwells on and as the eye-searing orb that lights him at his daily work; but man spiritual is as great as the universe—and greater!

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This book is part of the public domain. Garrett Putman Serviss (2022). Round the year with the stars. Urbana, Illinois: Project Gutenberg. Retrieved October 2022 https://www.gutenberg.org/cache/epub/68391/pg68391-images.html

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