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<v Speaker 1>Section twenty four of Sun, Moon and Stars Astronomy for Beginners.

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<v Speaker 1>This is a LibriVox recording. All LibriVox recordings are in

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<v Speaker 1>the public domain. For more information or to volunteer, please

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<v Speaker 1>visit LibriVox dot org. Praad by Prajakta. Sun Moon and

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<v Speaker 1>Stars Astronomy for Beginners by Agnes Gibben. Different kinds of sins,

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<v Speaker 1>great things do at kea which we cannot comprehend, Job

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<v Speaker 1>thirty seven five. Various in kind, various insights, various in color,

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<v Speaker 1>various in position, various in motion. Are the myriad suns

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<v Speaker 1>scattered through space? So far are they from being formed

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<v Speaker 1>on the same plan, turned out on the same model,

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<v Speaker 1>that it may, with reason be doubted whether any two

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<v Speaker 1>stars could be found exactly alike? Why should I expect

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<v Speaker 1>to find them? So no two oak leaves, no two

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<v Speaker 1>elm leaves precisely alike are to be found upon Earth.

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<v Speaker 1>So some stars are large, some are small, Some are

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<v Speaker 1>rapid in movement, some are slow. Some are yellow, some white,

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<v Speaker 1>some red, green, blue, purple, or green. Some are single stars.

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<v Speaker 1>Others are arranged in pairs, tears, quarter teaths, or groups.

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<v Speaker 1>Some appear only for a time, and then disappear altogether.

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<v Speaker 1>Others are changeful, with a light that regularly waxes and

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<v Speaker 1>veins in brightness. We have now give a little time

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<v Speaker 1>and thought to variable stars and temporary stars, afterwards to

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<v Speaker 1>double stars and colored stars. There are many stars which

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<v Speaker 1>pass through gradual and steady changes, first brightening, then less

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<v Speaker 1>in light, then brightening again. One such star is to

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<v Speaker 1>be seen in the constellation of the Veil. It is

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<v Speaker 1>named Mira, or the Marvelous, and the time in which

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<v Speaker 1>its changes take place extends to eleven months. For about

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<v Speaker 1>one fortnight, it is a star of the second magnitude.

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<v Speaker 1>Through three months, it grows slowly more and more dim

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<v Speaker 1>till it becomes invisible not only to the naked eye

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<v Speaker 1>but through ordinary telescopes. About five months it remains thus,

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<v Speaker 1>then again during three months it grows brighter and brighter

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<v Speaker 1>until it is once more a second magnitude star, and

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<v Speaker 1>after a fortnight's pause, begins anew to fade. There is

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<v Speaker 1>also a variable star in the constellation of Perseus, named

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<v Speaker 1>al Goal. The two waxes and vans regularly, but much

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<v Speaker 1>more rapidly, since it runs through its list of changes

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<v Speaker 1>in less than three days. It never becomes brighter than

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<v Speaker 1>a star of the second magnitude or dimmer than a

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<v Speaker 1>star of the fourth magnitude. Another variable star, Beetle Juice

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<v Speaker 1>in Orion, undergoes its variations in about two hundred days,

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<v Speaker 1>while yet another data CAPI takes only six days. Our

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<v Speaker 1>own sun has been reckoned, as in some slight degree

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<v Speaker 1>a variable star passing through his changes in eleven years.

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<v Speaker 1>When the sun spots are most numerous, he might appear, possibly,

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<v Speaker 1>if seen from a great distance, slightly more dim than

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<v Speaker 1>when there are none of them. Sometimes a new or

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<v Speaker 1>temporary star appears, blazing brightly for a brief space and

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<v Speaker 1>then vanishing. It may be a dim star already known,

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<v Speaker 1>which that's brings into a new and radiant phase of being,

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<v Speaker 1>Or it may be practically to us a new existence.

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<v Speaker 1>But doubtless the star was there before, a body too

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<v Speaker 1>faint for us to perceive, and doubtless it is there

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<v Speaker 1>still when the fires of its outbursts die away, once more,

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<v Speaker 1>too faint for its shining to reach our eyes. An

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<v Speaker 1>extraordinary specimen of a temporary star was seen in fifteen

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<v Speaker 1>seventy two. It was not a comet, for it had

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<v Speaker 1>no comma or tail. And it never moved from its place.

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<v Speaker 1>The brightness of the star was so great as to

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<v Speaker 1>surpass Serious and Jupiter, and to equal Venus at her

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<v Speaker 1>greatest brilliancy. Nay, it must have surpassed even Veners, for

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<v Speaker 1>it was plainly visible at midday in a clear sky.

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<v Speaker 1>Gradually the light faded and grew more dim till it

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<v Speaker 1>became a mere faint star. As it lasened in Brilliancy,

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<v Speaker 1>it also changed in color, passing from white to yellow,

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<v Speaker 1>and from yellow to red. This succession agrees with three

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<v Speaker 1>tints of the first, second, and fourth orders of suns,

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<v Speaker 1>as lately classified. Many other instances have been known. Beside

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<v Speaker 1>those referred to of variable and temporary stars. There are

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<v Speaker 1>two distinct kinds of double stars. First, we have those

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<v Speaker 1>which merely seem to be double, because one lies almost

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<v Speaker 1>directly behind the other, though widely distant from it, just

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<v Speaker 1>as a church tower two miles off may appear to

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<v Speaker 1>stand clothes side by side with another church tower two

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<v Speaker 1>and a half miles off, though they are in fact separated. Secondly,

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<v Speaker 1>we have the real systems of two sons belonging to

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<v Speaker 1>one another, the smaller moving round the larger, or more correctly,

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<v Speaker 1>both traveling around one central point called the center of gravity,

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<v Speaker 1>the smaller having the quicker rate of motion. Alpha Centauri

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<v Speaker 1>and sixty one Signy have been already described as examples

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<v Speaker 1>of true double stars. In the constellation Larry, a marked

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<v Speaker 1>instance is to be seen the brightest star in the

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<v Speaker 1>Larry is Vega, and near Vega shines a tiny star which,

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<v Speaker 1>to people with particularly clear sight has sometimes rather a

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<v Speaker 1>longish look. If you examine this star through an opera glass,

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<v Speaker 1>you will find it to consist of two separate stars.

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<v Speaker 1>But if you get a more powerful telescope and look again,

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<v Speaker 1>you will find that each star of the couple actually

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<v Speaker 1>consists of two stars. The four are not at equal distances.

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<v Speaker 1>Two points of light seemingly closed together, are parted by

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<v Speaker 1>a wide gap from two other points equally closed together.

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<v Speaker 1>These four stars are believed to have a double motion.

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<v Speaker 1>Each of the separate pairs revolves by itself the two

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<v Speaker 1>suns traveling around one center, and in addition to this,

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<v Speaker 1>the two couples of suns probably perform a long journey

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<v Speaker 1>around another center common to them all. Many thousands of

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<v Speaker 1>double stars have been discovered, and a large number of

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<v Speaker 1>these are now known to be not merely two distinctions

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<v Speaker 1>lying in the same line of sight, but to brother sons,

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<v Speaker 1>each probably the center of his own system of planets.

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<v Speaker 1>We have not only to consider the number of suns,

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<v Speaker 1>though of simple numbers, more yet remains to be said.

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<v Speaker 1>Attention must also be given to the varying colors of

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<v Speaker 1>different stars. For all suns in the universe are not

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<v Speaker 1>made after the model of arsin all suns are not yellow.

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<v Speaker 1>So far as single stars are concerned, colors seem rather limited.

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<v Speaker 1>White stars, golden or orange stars, ruby raid stars placed

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<v Speaker 1>alone are often seen, but blue stars, green stars, gray stars,

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<v Speaker 1>silver stars, purple stars are seldom, if ever visible to

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<v Speaker 1>the naked eye, are known to exist at single stars.

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<v Speaker 1>Take a powerful telescope and examine star couples, and a

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<v Speaker 1>very different result. You will find not white, yellow, and

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<v Speaker 1>red alone, but blue, purple, gray, green, fawn, buff, silvery, white,

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<v Speaker 1>and coppery youths will delight you in turn. As a rule,

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<v Speaker 1>when the two stars of a couple are alike in

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<v Speaker 1>they are either white or yellow or red. Also, in

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<v Speaker 1>the case of double stars of different colors, the larger

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<v Speaker 1>of the two is almost invariably white or some shade

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<v Speaker 1>of yellow. Or red. There are, however, exceptions to all

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<v Speaker 1>such rules. Blue stars are almost never seen alone, and

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<v Speaker 1>as one of a pair, the blue star is generally,

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<v Speaker 1>if not invariably, the smaller, But instances are known of

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<v Speaker 1>double stars, both of which are blue, and one group

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<v Speaker 1>in the southern Heavens is entirely made up of a

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<v Speaker 1>multitude of bluish sins. It is when we come to

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<v Speaker 1>consider double stars of two colors that the most striking

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<v Speaker 1>effects are found. Now and then, the two suns are

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<v Speaker 1>nearly the same in size, but more commonly one is

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<v Speaker 1>good deal larger than the other. This is known by

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<v Speaker 1>the brighter light of the larger and the more rapid

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<v Speaker 1>movements of the smaller. The laser star is often only

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<v Speaker 1>small by comparison, and maybe in reality a very goodly

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<v Speaker 1>and brilliant sun. Among nearly six hundred doubles examined by

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<v Speaker 1>one astronomer, there were three hundred and seventy five in

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<v Speaker 1>which the two stars were of one color, generally white, yellow, orange,

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<v Speaker 1>or red, the rest very different in tint, the difference

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<v Speaker 1>between the two sons in about one hundred and twenty

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<v Speaker 1>cases being very marked. For instance, a red primary as

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<v Speaker 1>the largest star is called will be seen with a

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<v Speaker 1>small green satellite, or a white primary will have a

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<v Speaker 1>little brother sun of purple, or of dark rubi, or

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<v Speaker 1>of light reed. Sometimes the larger sun is orange, the

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<v Speaker 1>company being purple or dark blue. Again, the chief star

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<v Speaker 1>will be red with a blue satellite, or yellow with

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<v Speaker 1>a green satellite, or orange with an emerald satellite, or

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<v Speaker 1>golden with a reddish green satellite. We hear of golden

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<v Speaker 1>and lilac couples, of cream and violet, pears, of white

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<v Speaker 1>and green companions, But indeed the variety is almost endless.

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<v Speaker 1>There may be worlds circling around these suns, worlds perhaps

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<v Speaker 1>with living creatures on them. We know little about how

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<v Speaker 1>such systems of suns and words may be arranged. Probably

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<v Speaker 1>each sun would have his own set of planets, and

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<v Speaker 1>both suns, with their planets, would travel round one central point,

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<v Speaker 1>perhaps where the second sun is much the smallest. It

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<v Speaker 1>might occasionally be like a big, pleasing satellite among the planets.

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<v Speaker 1>Among colored stars single and double, a few may be

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<v Speaker 1>mentioned by name as examples. Serious, as already observed, is

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<v Speaker 1>a brilliant white sun. The brilliant white also are Vega Canopus,

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<v Speaker 1>Regulus spica, and many others. Capella Prosian, the Pool Star,

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<v Speaker 1>and our own Sun are examples of yellow stars. Aldebaran, Beetle, Juice,

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<v Speaker 1>and Pollux are ruby red, and thees is a red

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<v Speaker 1>star with a greenish scintillation or change of view in

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<v Speaker 1>its twinkling. A tiny green sun belonging to this great

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<v Speaker 1>and brilliant rad sun has been discovered. Antares is sometimes

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<v Speaker 1>called the series of rad suns. The two double stars

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<v Speaker 1>sixty one Signy and Alpha Centauri are formed each of

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<v Speaker 1>two orange sons. In the Southern Cross, there is a

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<v Speaker 1>wonderful group of stars consisting of about one hundred and tensons,

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<v Speaker 1>nearly all invisible to the naked eye. Among the principal

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<v Speaker 1>stars of this group, which Sir John Herschel described as

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<v Speaker 1>being when viewed through a powerful telescope, like a casket

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<v Speaker 1>of variously colored precious stones, are two red stars, two

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<v Speaker 1>bright green, three pale green, and one of a greenish blue.

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<v Speaker 1>End of Section twenty four