Читать книгу The Friendly Stars - Martha Evans Martin - Страница 12
ОглавлениеVEGA
About three hours after Arcturus has risen there will come peeping over the northeastern horizon a brilliant, bluish star which twinkles so gayly and commands such instant admiration that its entrance into view has almost a dramatic effect. This is Vega, the third of the trio of bright stars that give a May-dance around the pole. Her companions, bright Capella and steady-shining Arcturus, are already gliding smoothly over the shining surface of the sky when she, clearing the tree-tops almost with a bound, lightly springs into view and the vernal festival is on.
The point on the horizon at which Vega makes her appearance is about fifty degrees from the pole. She lacks about seven degrees of being as far north as Capella, and is nearly twenty degrees farther north than Arcturus.
To find Vega, draw a line from the star at the junction of the bowl and the handle of the Dipper to Polaris. Then draw a line at right-angles to this nearly forty degrees in length and on the same side of the Dipper from which the handle projects, and it will point out the brilliant, beautiful Vega. The star is the only conspicuous one in the region described, and no other star can be mistaken for it.
Vega is on the opposite side of the pole from Capella, but the two stars are usually seen in the sky at the same time. In the spring, when Vega decks the eastern heavens, Capella glows in the northwest. In the autumn, when Capella comes sparkling over the dark purple sky in the northeast, Vega may be seen flying with its attendant stars down towards the northwest. Each one is hidden below the horizon for the few hours that the other holds the centre of the celestial stage and is at its highest point in its nightly course across the jewelled dome of the sky.
Making Vega the starting-point of measurement, Arcturus is about one-third of the way between Vega and Capella, though a little farther away from the pole. His part in the gay spring festivities is very conspicuous, and at that time the three stars are closely associated in their splendid, twinkling circuit around the pole which it may please our fancy to watch during the first soft nights of spring. In the autumn, when Vega and Capella have changed places in the evening skies, Arcturus is below the horizon and cannot be seen.
If one is in any doubt about the identity of Vega, it can always be recognized at a glance by the fact that there is following it four dainty stars arranged in an oblique parallelogram.
VEGA AS SHE APPEARS IN THE EAST
The position shown in the drawing is the one they always hold relative to Vega. When we see her in the east as she brightens the evening view in the spring and early summer the four stars are to the east of, or below, her; in the late autumn and winter, when the constellation is in the western sky, the position of the stars, as it appears to us, is partly reversed, and, with Vega leading them towards the northwestern horizon, they appear as shown in the illustration.
VEGA AND HER ATTENDANT STARS IN THE NORTHWEST
Vega, like Capella, can be seen in our latitude at some time during the night every night in the year. One can see it even between sunset and midnight every night in the year. But to do this it will be necessary to keep a sharp lookout low in the northwest very early in the evenings in February and to turn just as sharp eyes towards the northeast between eleven and twelve o'clock in the early part of March. As April progresses the star more and more asserts its supremacy in the northeastern heavens. During the latter part of this month and all of May it is singularly beautiful as it passes almost airily between us and the rich dark background so full of color characteristic of the spring-time sky.
Vega is the chief star in the constellation called the Lyre—once fancied to be the magic lyre which in Orpheus's hands gave forth music that tamed wild beasts and chained the rivers in their courses. It is easy to get some sense of the fancy that gave the constellation its name as we watch it during the lovely spring evenings floating lightly in the sky, the parallel lines connecting its principal stars vaguely suggestive, to the willing mind, of some quaint stringed instrument that under a magic touch might send out heavenly music through the resonant air.
Early in May the star rises at about the same hour that the sun sets, and all summer long it is the gayest and perhaps the most instantly attractive star in the evening skies. It is the star so often noticed and commented on as shining with great brilliancy directly overhead between nine and ten o'clock during the hot summer evenings of July and August. When autumn comes it has passed the highest point in its journey across the heavens and may be seen travelling towards the northwest. Here it shines splendidly during the early evening, setting in December somewhere near eleven o'clock and in January about nine. It is above the horizon eighteen hours out of each twenty-four and rises six hours after it has set.
Vega is the most brilliant star in the skies of the northern hemisphere, though its supremacy is closely contested by Capella and Arcturus. There are only three stars in the entire heavens, north or south, that are brighter. These are Sirius, Canopus, and Alpha Centauri, all stars of the southern hemisphere. Sirius, as we know, can be seen in our latitude, but it lies south of the celestial equator, and is, therefore, called a southern star. The other two lie so far south that they do not come within our view.
Vega is one of the very large suns of the universe and gives out about ninety times as much light as our sun. Its distance is such that it requires about twenty-nine years for light to travel from it to us, which shows it to be somewhat nearer to us than Capella and very much nearer than Arcturus. It is coming nearer all the time, too. Thirty-four miles a second is about the rate at which it is approaching us; but, as we have already seen, it will take many centuries for even such almost incredible speed as that to make any appreciable difference to us in the brightness of a star.
Vega is the same type of star as Spica. It is in a much earlier stage of development, and, consequently, is a much less solid body than either Capella or Arcturus. It is also less hot than either of these two stars; for they are like our sun, and the solar type of star is now supposed to be at its hottest stage.
Vega has a companion star, much smaller than itself, revolving around it, which is of the same beautiful bluish color as the larger star. The companion is of about the tenth magnitude and can be seen only with a large telescope. Vega is about four thousand times brighter than her companion.
One of the most interesting things about Vega is that it seems to mark, or nearly mark, the point towards which our sun with all his planets is travelling.
