Star system

“ In like manner, when we pass in imagination beyond the limits of our own system, we may learn a useful lesson from the imagined creatures' reasoning about other tree systems than that to which their world belonged. Astronomers have been apt to generalise too daringly respecting remote stars and star systems, as though our solar system were a true picture of all solar systems, the system of stars to which our sun belongs a true picture of all star systems. ”

“ This vast system of stars resembles a gigantic sidereal billow flowing towards the Milky Way as towards some mighty shore-line. Nor is this description altogether fanciful; since one of the most marked instances of star-drift presently to be adduced refers to this very region. These associated stars are urging their way towards the galaxy, and that at a rate which, though seemingly slow when viewed from beyond so enormous a gap as separates us from this system, must in reality be estimated by millions of miles in every year. ”

“ We have traversed a distance which even on [Pg 135] the wings of light we could only accomplish in many thousands of years, and now stand on the outskirts of our great star cluster, in the same way, and I hope with the same aspirations, as when we paused the last time on the confines of our Solar System. Behind us are myriads of shining orbs, in such countless numbers that human thought cannot even suggest a limit, and yet each of these is a mighty globe like our Sun, the centre of a planetary system, dispensing light and heat under conditions similar to what we are accustomed to here. ”

“ The motions which the telescope uncovers may decide in favor of a central attraction, but it is silent as to the intensity of this attraction unless the moving body belongs to the solar system. The universality of a gravitation may be proved, but not the universality of the very gravitation which pervades our own system, except by an argument from analogy. We see that one star differs from another star in glory. But what the other differences or resemblances are we know not, without the spectroscope. ”

“ B. True, but then the distance of the fixed stars is so immense, that our solar system is in comparison to it but a spot, and the whole extent of the earth's orbit but a point; therefore, whether the earth remain stationary, or whether it revolved in its orbit during its rotation on its axis, no sensible difference would be produced with regard to the fixed stars. One complete revolution brings the same meridian back to the same fixed star; hence the fixed stars appear to go round the earth in a shorter time than the sun by three minutes fifty-six seconds of time. ”

“ If we assume that around each of the components of a multiple star there circles a retinue of planetary worlds, we are confronted with a most perplexing problem as to how the dynamical stability of a system so different from, and so vastly more complicated than, that of our solar system is maintained—where, as it were, suns and planets intermingle—how numerous circling orbs can accomplish their revolutions without being swayed and deflected from their paths by the gravitational attraction of adjacent members of the same system. ”

“ Granting that, in the general average, each star is as bright as the sun, and that their thickness is such that within a sphere of 3300 light-years there are 1,000,000,000 stars, if we inquire how far out such a system must be continued in order that the sky shall shine with even four per cent of the light of the sun, we shall find the distance of its boundary so great that millions of millions of years would be required for the light of the outer stars to reach the centre of the system. ”

“ Our knowledge of binary star systems brings us to what may be regarded as the threshold of the fabric of the heavens. For it is known that other systems exist into the construction of which numerous stars enter. These form intricate and complex stellar arrangements, in which the component stars are physically united and retained in their orbits by their mutual attraction. ”

“ Our distance from the sun shrinks up into a mere speck—the whole solar system into a mere unit of measurement, to be repeated hundreds of thousands of times before we reach the stars.
Yet their motion is visible—yes, to very accurate measurement quite plain. One star, known as 61 Cygni, was then and is now rushing along at the rate of 100 miles every second. Not that you must imagine that this makes any obvious and apparent change in its position. No, for all ordinary and practical purposes they are still fixed stars; thousands of years will show us no obvious change ”

“ If the stars were at rest, or if a sufficient number of stars were taken to eliminate the consequences of their individual motions, then the spectroscopic search for the movements of the solar system becomes very simple. It is only necessary to measure the rate at which the solar system alters its distance from the various points around. That point on the celestial sphere where the star shows the velocity of approach to be greatest, can only be the point towards which the solar system is directing its motion. ”

“ One thing, however, is fully ascertained by the observations which have been made to find the parallax of the stars, which is, that they are so immensely distant from our planetary regions, that the whole solar system, consisting of the sun and planets, with their satellites, and the comets, would, if viewed from the nearest fixed star, appear as crowded into one single point of space, which is also known from other observations. ”

“ We have said the stars are not uniformly distributed in space. Their concentration in the Milky Way, forming a narrow band dividing the sky into two very nearly equal parts, must be due to their being actually massed in a thin disk or ring of space within which our solar system is also situated. This thin disk projected upon the sky would then appear as the narrow star-band of the Milky Way. Now, suppose this disk has an axis perpendicular to itself, and let us imagine a rotation of the whole sidereal system about that axis. ”

“ The system of star-gauging, which the Herschels did little more than illustrate (as Sir W. Herschel himself admitted) , should be applied with telescopes of different power to the whole heavens, [4] not to a few telescopic fields. Processes of charting, and especially of equal surface charting, should be multiplied. Fresh determinations of proper motions should be systematically undertaken. All the evidence, in fine, which we have, should be carefully examined, and no efforts should be spared by which new evidence may be acquired. ”

“ They form a sequel to his father's labours such as the investigations of one man have rarely received from those of another. What the elder observer did for the northern heavens, the younger did for the southern, and with generally concordant results. Reviving the paternal method of "star-gauging," he showed, from a count of 2,299 fields, that the Milky Way surrounds the solar system as a complete annulus of minute stars ”

“ But the difficulty is that the part of the stellar universe which we mainly survey is a local condensation or star-cloud forming part of a much greater system. In certain directions in the sky our telescopes penetrate to the limits of the system, but in other directions the extent is too great for us to fathom. The Milky Way, which on a dark night forms a gleaming belt round the sky, shows the direction in which there lie stars behind stars until vision fails. ”

“ If I am right, the external star-systems lie far beyond the reach of the most powerful telescope man has yet been able to construct, insomuch that perchance the nearest of the outlying galaxies may lie a million times beyond the range even of the mighty mirror of the great Rosse telescope. ”

“ As the accuracy attainable improves with experience, the proportional number of spectroscopic binaries discovered will undoubtedly be enormously increased. In fact, the star which seems not to be attended by dark companions may be the rare exception. There is the further possibility that the stars attended by massive companions, rather than by small planets, are in a decided majority; suggesting, at least, that our solar system may prove to be an extreme type of system, rather than a common or average type. ”

“ The whole mass of the stellar system exerts a gravitational influence on the motion of each star in the system, and the individual stars revolve around the center of mass of the system in their elongated orbits. One star stream comprises all those stars moving away from the center, and the other stream all those stars moving toward the center. We can not doubt that the motions of the individual stars are influenced by the gravitational attractions of the stellar system and of the group of stars nearest to them ”

“ It has been one of the most difficult problems of cosmogony to form a theory to63 account for the origin of the Galactic system. We may, almost yearly, witness how new stars blaze into existence only to fade rapidly and in a few years return to their old insignificance—that is, they become invisible to the naked eye although through powerful lenses we may frequently discover an exceedingly faint star in their position. ”

“ The two components, under the influence of powerful mutual gravitational attraction, must be revolving in a mighty orbit. Yet this vast orbit, as a whole, with the two great stars in it, must be approaching our part of the universe all the time. For the spectroscope shows the velocity of approach to increase and diminish, indeed, but it is always present. Here, then, is this great stellar system, having a four-day revolution of its own, and yet swinging rapidly through space in our direction. Nor is this all. One of the component stars must be nearly or quite dark ”

“ But smaller instruments reveal only the in-running star streams and the sprinkling of stellar points over the main aggregation, which cause it to sparkle like a cloud of diamond dust transfused with sunbeams. The appearance of flocking together that those uncountable thousands of stars present calls up at once a picture of our lone sun separated from its nearest stellar neighbor by a distance probably a hundred times as great as the entire diameter of the spherical space within which that multitude is congregated. ”

“ But since they vastly outnumber the binary and multiple systems, and since they resemble the sun in [Pg 190] having no large attendants, should we be justified, after all, in regarding our system as "unique"? It is true we do not know, by visual evidence, that the single stars have planets, but we find planets attending the only representative of that class of stars that we are able to approach closely—the sun—and we know that the existence of those planets is no mere accident, but the result of the operation of physical laws which must hold good in every instance of nebular condensation. ”

“ A proper motion in space of our sun, and of the fixed stars as we call them, has long been believed to exist. Their vast distances only prevent its being more apparent. The great improvement of instruments of measurement within the last generation has not only established the existence of this motion, but has pointed to the region in the starry vault around which our whole solar and stellar system, with its myriad of attendant planetary worlds, appears to be performing a mighty revolution. ”

“ The paths of the planets and comets round the Sun, and of the satellites round their planets, are called their ORBITS.
Those stars which always appear in the same situation in relation to each other are called Fixed Stars. About 1000 can be seen at once by the naked eye, and by the help of the telescope many millions may be seen. Their sizes are little known, but probably some of them are many million times larger than the earth. They are not considered a part of our Solar System, but are supposed to be Suns of other systems, round which other planets revolve. ”

“ Imagine that every one of those grains of pepper was to be transformed into a tiny electric light, and then you have some idea of what a cluster of stars would look like when viewed through a telescope of sufficient power. There are multitudes of such329 groups scattered through the depths of space. They require our biggest telescopes to show them adequately. We have seen that our sun is a star, being only one of a magnificent cluster that form the Milky Way. ”

“ The Sun, however, doesn’t have a stellar neighbor, but only planets. The binary stars can have different separations or orbits, and these are oriented randomly in the sky. Since there are many stars in our Galaxy, some binary stars orbit a plane very aligned with the Earth, so then, in a particular region of its orbit, a star passes in front of the other, blocking the brightness of the one in the back. ”

“ 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. ”