SECT. II.
Of the Fixed Stars.
The fixed Stars are at immense distance from us.
The fixed Stars are those bright and shining bodies, which in a clear night appear to us every where dispersed through the boundless regions of space. They are term’d fix’d, because they are found to keep the same immutable distance one from another in all ages, without having any of the motions observed in the Planets. The fixed Stars are all placed at such immense distances from us, that the best of telescopes represent them no bigger than points, without having any apparent diameters.
The fixed Stars are luminous bodies like the Sun.
It is evident from hence, that all the Stars are luminous bodies, and shine with their own proper and native light, else they could not be seen at such a great distance. For the Satellites of Jupiter and Saturn, tho’ they appear under considerable angles through good telescopes, yet are altogether invisible to the naked eye.
The distance from us to the Sun is nothing in comparison of the vast distance of the fixed Stars.
Although the distance betwixt us and the Sun is vastly large, when compared to the diameter of the Earth, yet it is nothing when compared with the prodigious distance of the fixed Stars; for the whole diameter of the Earth’s annual orbit, appears from the nearest fixed Star no bigger than a point, and the fixed Stars are at least 100,000 times farther from us than we are from the Sun; as may be demonstrated from the observation of those who have endeavoured to find the Parallax of the Earth’s annual Orb, or the angle under which the Earth’s orbit appears from the fixed Stars.
As to appearance, the Earth may be consider’d as being the center of the Heavens.
Hence it follows, that tho’ we approach nearer to some fixed Stars at one time of the year than we do at the opposite, and that by the whole length of the diameter of the Earth’s orbit; yet this distance being so small in comparison with the distance of the fixed Stars, their magnitudes or positions cannot thereby be sensibly altered; therefore we may always, without error, suppose ourselves to be in the same center of the Heavens, since we always have the same visible prospect of the Stars without any alteration.
The fixed Stars are Suns.
If a spectator was placed as near to any fixed Star, as we are to the Sun, he would there observe a body as big, and every way like, as the Sun appears to us: and our Sun would appear to him no bigger than a fixed Star: and undoubtedly he would reckon the Sun as one of them in numbering the Stars. Wherefore since the Sun differeth nothing from a fixed Star, the fixed Stars may be reckoned so many Suns.
The fixed Stars are at vast distance from each other.
It is not reasonable to suppose that all the fixed Stars are placed at the same distance from us; but it is more probable that they are every where interspersed thro’ the vast indefinite space of the universe; and that there may be as great a distance betwixt any two of them, as there is betwixt our Sun and the nearest fixed Star. Hence it follows, why they appear to us of different magnitudes, not because they really are so, but because they are at different distances from us; those that are nearest excelling in brightness and lustre those that are most remote, who give a fainter light, and appear smaller to the eye.
The distribution of the Stars into 6 classes.
Of Telescopical Stars.
The astronomers distribute the Stars into several orders or classes; those that are nearest to us, and appear brightest to the eye, are called Stars of the first magnitude; those that are nearest to them in brightness and lustre, are called Stars of the second magnitude; those of the third class, are stiled Stars of the third magnitude; and so on, until we come to the Stars of the sixth magnitude, which are the smallest that can be discerned by the naked eye. There are infinite numbers of smaller Stars, that can be seen through telescopes; but these are not reduced to any of the six orders, and are only called Telescopical Stars. It may be here observed, that tho’ the astronomers have reduced all the Stars that are visible to the naked eye, into some one or other of these classes, yet we are not to conclude from thence that all the Stars answer exactly to some or other of these orders; but there may be in reality as many orders of the Stars, as they are in number, few of them appearing exactly of the same bigness and lustre.
The Stars digested into constellations
The ancient astronomers, that they might distinguish the Stars, in regard to their situation and position to each other, divided the whole starry firmament into Several Asterisms, or systems of Stars, consisting of those that are near to one another. These Asterisms are called Constellations, and are digested into the forms of some animals; as Men, Lyons, Bears, Serpents, &c. or to the images of some known things; as, of a Crown, a Harp, a Triangle, &c.
Zodiac.
The starry firmament was divided by the ancients into 48 images, or constellations; twelve of which they placed in that part of the Heavens wherein are the planes of the Planetary orbits; which part is called the Zodiac, because most of the constellations placed therein resemble some living creature. The two regions of the Heavens that are on each side of the Zodiac, are called the North and South parts of the Heavens.
Constellations within the Zodiac.
The constellations within the Zodiac are, 1. Aries, the Ram; 2. Taurus, the Bull; 3. Gemini, the Twins; 4. Cancer, the Crab; 5. Leo, the Lion; 6. Virgo, the Virgin; 7. Libra, the Balance; 8. Scorpio, the Scorpion; 9. Sagittarius, the Archer; 10. Capricornus, the Goat; 11. Aquarius, the Water-Bearer; and, 12. Pisces, the Fishes.
Northern constellations.
The constellations on the North side of the Zodiac are Twenty-one, viz. the Little Bear; the Great Bear; the Dragon; Cepheus, a king of Ethiopia; Bootes, the keeper of the Bear; the Northern Crown; Hercules with his Club, watching the Dragon; the Harp; the Swan; Cassiopeia; Persius; Andromeda; the Triangle; Auriga; Pegasus, or the Flying Horse; Equuleus; the Dolphin; the Arrow; the Eagle; Serpentarius; and the Serpent.
Southern constellations.
The constellations noted by the ancients on the South side of the Zodiac, were fifteen, viz. the Whale; the river Eridanus; the Hare; Orion; the Great Dog; Little Dog; the Ship Argo; Hydra; the Centaur; the Cup; the Crow; the Wolf; the Altar; the Southern Crown; and the Southern Fish. To these have been lately added the following, viz. The Phœnix; the Crane; the Peacock; the Indian; the Bird of Paradise; the Southern Triangle; the Fly; Cameleon; the Flying Fish; Toucan, or the American Goose; the Water Serpent, and the Sword Fish. The ancients placed those particular constellations or figures in the Heavens, either to commemorate the deeds of some great man, or some notable exploit or action; or else took them from the fables of their religion, &c. And the modern astronomers do still retain them, to avoid the confusion that would arise by making new ones, when they compare the modern observations with the old ones.
Unformed Stars.
Some of the principal Stars have particular names given them, as Syrius, Arcturus, &c. There are also several Stars that are not reduced into constellations, and these are called Unformed Stars.
The Galaxy, or Milky Way.
Besides the Stars visible to the naked eye, there is a very remarkable space in the Heavens, called the Galaxy, or Milky Way. This is a broad circle of a whitish hue, like milk, going quite round the whole Heavens, and consisting of an infinite number of small Stars, visible thro’ a telescope, tho’ not discernable by the naked eye, by reason of their exceeding faintness; yet with their light they combine to illustrate that part of the Heavens where they are, and to cause that shining whiteness.
The places of the fixed Stars, or their relative situations one from another, have been carefully observed by astronomers, and digested into catalogues. The first among the Greeks, who reduced the Stars into a catalogue, was Hypparchus, who, from his own observations, and of those who lived before him, inserted 1022 Stars into his catalogue, about 120 years before the Christian Æra: This catalogue has been since enlarged and improved by several learned men, to the number of 3000, of which there are a great many telescopical, and not to be discerned by the naked eye; and these are all ranked in the catalogue as the Stars of the seventh magnitude.
It may seem strange to some, that there are no more than this number of Stars visible to the naked eye; for sometimes in a clear night they seem to be innumerable: but this is only a deception of our sight, arising from their vehement sparkling, while we look upon them confusedly, without reducing them into any order; for there can seldom be seen above 1000 Stars in the whole Heavens with the naked eye at the same time; and if we should distinctly view them, we shall not find many but what are inserted upon a good Celestial Globe.
Altho’ the number of Stars that can be discerned by the naked eye are so few, yet it is probable there are many more which are beyond the reach of our optics, for through telescopes they appear in vast multitudes, every where dispersed throughout the whole Heaven; and the better our glasses are, the more of them we still discover. The ingenious Dr. Hook has observed 78 Stars in the Pleiades, of which the naked eye is never able to discern above 7; and in Orion, which has but 80 Stars in the British catalogue (and some of them telescopical) there has been numbered 2000 Stars.
An idea of the Universe.
Those who think that all these glorious bodies were created for no other purpose than to give us a little dim light, must entertain a very slender idea of the Divine Wisdom; for we receive more light from the Moon itself, than from all the Stars put together. And since the Planets are subject to the same laws of motion with our Earth, and some of them not only equal, but vastly exceed it in magnitude, it is not unreasonable to suppose, that they are all habitable Worlds. And since the Fixed Stars are no ways behind our Sun, either in bigness or lustre, is it not probable, that each of them have a system of Planetary Worlds turning round them, as we do round our Sun? And if we ascend as far as the smallest Star we can see, shall we not then discover innumerable more of these glorious bodies, which now are altogether invisible to us? And so ad infinitum, thro’ the boundless space of the universe. What a magnificient idea must this raise in us of the Divine Being! Who is every where, and at all times present, displaying his Divine Power, Wisdom and Goodness, amongst all his Creatures!
The DESCRIPTION and USE of the
Celestial and Terrestrial Globes.
Globe or Sphere.
A Globe or Sphere is a round solid body, having every part of its surface equally distant from a point within it, called its Center; and it may be conceived to be formed by the revolution of a semicircle round its diameter.
Great Circle.
Hemispheres.
Any circle passing through the center of the sphere, thereby dividing into two equal parts or segments, is called a Great Circle; and the segments of the sphere so divided, are called Hemispheres.
Every great circle has its Poles and Axis.
Poles.
The Poles of a great circle are two points on the surface of the sphere, diametrically opposite to one another, and every where equally distant from the said circle.
Axis.
The Axis of a circle is a right line passing through the center of the sphere, and through the Poles of the said circle, and is therefore perpendicular to the Plane: Therefore
Secundaries.
All circles passing through the Poles of any great circle, intersect it in two places diametrically opposite, and also at right angles; and with respect to the said great circle, they may be called its Secundaries.
Parallel or lesser Circles.
All circles dividing the sphere into two unequal parts, are called lesser or parallel Circles, and are usually denominated by that great circle to which they are parallel.
Terrestrial Globe.
The Earth being globular, its outward parts, as the several Countries, Seas, &c. are best, and most naturally represented upon the surfaces of a Globe; and when such a body has the outward parts of the Earth and Sea delineated upon its surface, and placed in their natural order and situation, it is called a Terrestrial Globe.
Celestial Globe.
The Celestial Bodies appear to us as if they were all placed in the same concave sphere, therefore astronomers place the Stars according to their respective situations and magnitudes, and also the images of the constellations, upon the external surface of a Globe; for it answers the same purposes as if they were placed within a concave sphere, if we suppose the Globe to be transparent, and the eye placed in the center. A Globe having the Stars placed upon its surface, as above described, is called a Celestial Globe. These Globes are both placed in frames, with other appurtenances, as shall be described in a proper place.
The principal use of the Globes.
The principal uses of the Globes (besides their serving as Maps, to distinguish the outward parts of the Earth, and the situations of the fixed Stars) is to explain and resolve the phænomena arising from the diurnal motion of the Earth round its Axis.
There will be the same prospect of the fixed Stars whether the spectator be placed on the Earth, or in the Sun.
It has been shewed in the Introduction, that the distance of the Earth from the Sun, is no more than a point, when compared with the immense distance of the fixed Stars; therefore let the Earth be in what point soever of her orbit, there will be the same prospect of the Heavens, as a spectator would observe did he reside in the Sun: And if several circles be imagined to pass thro’ the center of the Earth, and others, parallel to them, be conceived to pass thro’ the center of the Sun, these circles in the Heavens will seem to coincide, and to pass exactly thro’ the same Stars. Wherefore as to the appearances of the fixed Stars, it is indifferent whether the Earth or the Sun be made the center of the Universe. But because it is from the Earth that we always observe the celestial bodies, and their apparent motions seem to us to be really made in the Heavens, it is more natural in explaining the phænomena arising from these motions, to place the Earth in the center. And again, because the semidiameter of the Earth, when compared to her distance from the Sun, is of no sensible magnitude, any point, upon the Earth’s surface, let her be in what part soever of the orbit, may be considered as being the center of the Universe. Upon these principles, the different phænomena arising from the diurnal motion of the Earth, and the different situation of a spectator upon its surface, are very naturally illustrated and explained by the Globes.
As to the alterations of seasons, &c. arising from the annual motion of the Earth round the Sun, it is indifferent which we suppose to move, the Earth or the Sun, for in both cases the effect will be the same. Wherefore because it is the Sun that appears to us to move, we say the Sun is in such a part of the ecliptic, without attributing any motion to the Earth, any more than if she had actually been at rest. For the same reason we say the Sun rises, or the Sun sets; by which we mean that he begins to appear or disappear, without considering in the least how these effects are produced. These things are here mentioned, to obviate the objections that might be made by beginners, after they have been told that the Sun stands still.
