Читать книгу The Friendly Stars - Martha Evans Martin - Страница 9
ОглавлениеCAPELLA
Capella is a charming star that has the distinction of being situated nearer to the North Star than any other of the brightest stars. It can be found by drawing a line forty-five degrees long from Polaris at a right angle to the line from the pointers to the pole and running in an opposite direction from the handle of the Dipper. It is also pointed out by a line starting at the star which marks the bottom of the Dipper on the handle side and running thence about half-way between the two pointers, for a distance of about fifty degrees, or to the first bright star, which is Capella. If these directions are even approximately followed Capella can be discovered, for there is no other star in its neighborhood that in any way compares with it in brightness.
Capella is one of the most brilliant stars in the heavens. Not many years ago it was classed by the best authorities as the brightest in the northern hemisphere of the skies. Sirius, as we know, always shines with greater brilliancy than any other star; but Sirius lies south of the equator and does not belong among the stars of the northern hemisphere, although in our latitude it, fortunately, can be seen.
In recent years, however, possibly on account of a real change in brilliancy, but probably by reason of more delicate measurements of its light, Capella has been found to be very slightly less lustrous than one other bright star that is classed as northern. The difference is so trifling that it might well be questioned by an ordinary observer, and is really not of much importance since the two stars are so nearly equal in brilliancy and each in its way has its own peculiar charm.
Being so far north, Capella is above the horizon more than twenty hours out of each twenty-four, so that it can be seen at some time in the night every month in the year, and one comes to be on most familiar and friendly terms with its bright face. Its first appearance in the skies of the early evening is in August, when it rises about ten o'clock during the first half of the month; and it remains a constant ornament of the nights until the latter part of the following June. July is the only month in which it does not show its face at some time before midnight; and even in July, if one watches closely late in the month, he can have glimpses of the star following the evening sun at no great distance and almost lost in the sunset glow. In October it rises just as the sun is setting.
Capella rises almost exactly in the northeast and swings in a fine long circle over the heavens during its twenty-hour journey to the northwest, where it sets for a brief time, and then rises again in about four hours.
When you watch the birds congregating in noisy flocks in the morning for the fall migration, and in the afternoon gather the first fringed gentians, look for Capella in the northeastern sky in the evening. When the trees are bare and the berries are wrapped in ice and snow, so that the winter birds greedily gather what in your bounty you throw to them, you will find Capella shining almost directly overhead early in the evening. During the spring months, when the air is full of the stir of the awakening earth, and other stars are demanding our attention to their return in the east after long absences, Capella is hurrying on towards the northwest, no longer charming us with its novelty, but still as bright and fair as ever and ready to fill its place in the brilliant gathering of the stars of spring.
Capella is yellow in color like our sun (which is a star). In its life as a star it is at about the same stage of existence as the sun and shows about the same chemical composition. Being of the same type as the sun, it gives something near an equal amount of heat and light in proportion to its size. But it is so much larger than our sun that it really gives out at least one hundred and twenty times more light. Its distance is so great that its light requires nearly forty years to reach us in its journey through space, though travelling, as light does, with a swiftness of about 186,000 miles a second. At the distance of the nearest fixed star, our beautiful big sun would shine as a star no brighter than Polaris. But Capella is nine times farther away than the nearest fixed star, and still shines as one of the brightest of the bright stars. If Capella were inhabited, our sun would appear to its people as one of the faintest stars that we can see with ease. But it is not inhabited, for it is a very hot, rarefied and expanded body, as much as forty times rarer than our sun, and like the other bright stars, no place for the existence of life as we know it.
It has been discovered in recent years that Capella is not alone as it makes its journey through the black void. Like so many other stars, it is what is known as a binary system, or a double star, and has a companion which lies so near it that they circle around each other in a little more than a hundred days, or less than one-third of the time that it takes the earth to go around the sun.
Capella and its companion have never been seen separately even with the assistance of the strongest telescope. But the wizard spectroscope has penetrated their family secret and by its means astronomers have learned that they are two immense, fiery bodies of nearly the same size and perhaps a hundred times more voluminous than the sun, whirling with incredible speed about each other. The diameter of the orbit over which the two stars spin is so large that we could string more than a hundred suns along it and still have room left for a few more shining beads of the same sort.
Since it has been known that Capella is a double star it has been seen through at least one telescope as oval instead of round, showing that the two stars have been caught at a place in their orbit where they appeared side by side to our view.
These are interesting facts that science has to tell us about Capella; but the star that fixes itself in our regard is the fair, golden, bright Capella that decks the sky in its season. We follow it in its course visible to us across the heavens, we joy in its beauty and feel the kindly influence that astrologers have always ascribed to it, and find its gentle light no less gentle on account of its being the composite of the great orbs we know it is.
Capella is at present receding from us at the rate of about twenty miles a second, or more than a million miles a day. At first thought this rather makes us fear that we are in danger of losing this beautiful star from view. But it will be many hundreds of years before even under such speeding away there will be any appreciable change in its brightness.
The constellation of which Capella forms a part is called Auriga. It is a five-sided figure somewhat in the shape of a shield. It can be easily recognized as soon as Capella is located. It will be described among the constellations later on.
