Part 24

"Some of the natives of Australia believe that when the flowers die on earth they rise on the winds and float away to the fair fields of heaven, where they flourish forever in immortal beauty. We cannot see the colors of these flowers of heaven very well, on account of the air that surrounds the earth. If it were removed, then the dark sky would seem to be covered with starry flowers of all the colors of the rainbow."

"How beautiful!" said Harry thoughtfully. "How I wish we could see them that way!"

"But even as it is," said his sister, "you can see some of these colors. Look at white Sirius, that sometimes seems to me tinged with blue, and then at red Aldebaran in the eye of the bull, and a creamy star called Capella just near the Twins. So you can see some of the colors. And now a few more words about Castor, which is a double star. That is, it is made up of two bright stars, and they go around each other.

"Professor Ball was once showing the stars through his telescope to some friends, when he pointed out this double star to them. First of all, he told them to note the different colors of the stars, for one was white, the other green. All double stars are of complementary colors. One may be green and the other red, one blue and the other orange.

"Then Professor Ball told his visitors that the stars went round each other.

"'Oh, yes!' said one of the visitors. 'I saw them going round in the telescope.'

"But it was the twinkling that made the stars appear to dance around each other. In reality, he would have had to remain with his eye at the telescope more than a hundred years before he could have seen the stars go completely around each other."

NUMBER OF THE STARS.

"I wonder how many stars there are in the sky, sister," said Harry. "Do you think we could count them?"

"I read somewhere," replied his sister, "that the stars are as plentiful as the sands on the seashore. Still, in the whole sky, the number bright enough to be seen without a telescope is only from six to seven thousand in a clear, moonless sky. With an opera glass you can bring the number up to one hundred thousand. A small telescope can show about three hundred thousand, while with a telescope such as the one at the Lick Observatory the number would be nearly one hundred million. But it is possible to photograph the stars, and millions of stars have had their pictures taken. Probably we would never have known anything about them but the camera caught them, and now they are being named and labeled, so that they cannot escape us again. In fact, some of the stars are so far away that if we had not captured them in this way they would have remained hidden to us forever."

"What do you mean, sister?" said Harry, his eyes filled with surprise.

"I mean, dear, that some stars are so far away that their light has not yet reached us. Don't you remember what I told you about Jupiter's moons: that they are so far away that light takes about half an hour in coming from them to the earth. Well, the stars are hundreds of times as far away as Jupiter's moons. So far away are they that even from the nearest--a star seen in the southern hemisphere--light takes four years and four months in reaching us, although light travels more than 186,000 miles a second."

DISTANCE OF THE STARS.

"Look at the Pole Star some night, and you will not see it as it is now, but as it was more than sixty-two years ago. All this time its light has been on its way to Planet Earth. If a planet travels around the Pole Star, or Polaris, as it is sometimes called, and an astronomer on that planet looked at the earth he would not see it as it is now, but as it was more than sixty-two years ago. There are other stars so far away that light takes hundreds of years in coming here. Perhaps they faded out long ago, but the message is still on its way. It does seem strange to think of people who may be living on distant worlds in space, watching our little world, but we need not fear. The earth is so small that it could not be seen at all, even from the nearest star. At that distance Giant Sun would not look quite as bright as Sirius does to us, and giant Planet Jupiter would only appear as a faint speck of light near the sun."

"How far away everything seems to be!" said Harry. "Yet you said just now that we could tell what the stars are made of. How can we do that?"

WHAT ARE THE STARS MADE OF?

"The stars are made of iron, copper, zinc, and other such metals, but the heat is so intense that these metals are turned into vapor. You have seen the steam coming from the spout of a kettle when water is boiling, and you know then that the water is scalding hot. But imagine heat so great that masses of iron and copper are not only melted but turned into vapor. Then you have some idea of the intense heat that prevails on the stars. The rains that fall on earth are made up of drops of water, but the rainfalls on the stars must be drops of melting iron, while the clouds that form are sheets of molten metal."

"How wonderful!" said Harry; "and how do we know this, as the stars are so far away?"

"By means of a little instrument known as the spectroscope, or light-sifter. But you must wait till you are a little older before I can explain that to you, as it is something very difficult to understand. At any rate, I can tell you this, that when we want to find out what a star is made of we catch a ray of its light and examine it with the light-sifter. As Professor Ball quoted in one of his lectures:

"'Twinkle, twinkle, little star, Now we find out what you are, When unto the midnight sky We the spectroscope apply.'"

"And can you tell how old the stars are?" asked Harry; "because when you were talking about the planets you said some are old and some are young."

"This same little spectroscope tells us that as well, and we can recognize the stars that are in their infancy, and others that are middle-aged or nearly worn-out."

"How strange to think of worn-out stars," said Harry; "yet I suppose they must grow old sometime, just as we do; only I suppose they take ever so much longer growing up."

"Hundreds of years," said Mary, laughing at the idea of grown-up stars. "There are young stars and old stars, and even the star that gives us light and heat will grow cold and dead some day, and not warm its planets any longer. But that will be millions of years hence, long after we are dead and gone."

OUR ISLAND UNIVERSE.

"So it is all over the heavens. Our little universe is like an island in space. There are other islands like our own, with their millions of stars and star-clusters and star-mist, passing through the periods of youth, middle age, old age, and decay. Our little universe is not eternal. It cannot last forever, but as long as it does we should feel glad that we are here to enjoy it.

"Now, Harry, I really think we have had quite a long ramble in starland for one evening, and I believe two little stars I know need a rest."

"They are a little tired," said Harry, smiling; "two little worn-out stars, sister; and perhaps they do want to let the curtains down over them for awhile."