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The Dipper is only one of several constellations near the North Star. Another one is the Little Dipper; this is a part of the Little Bear. The North Star is at the end of the Little Dipper's handle, or at the end of the Little Bear's tail. See the star map (Fig. 57, a and b) in this chapter.

Let us look for another constellation. Imagine a circle in the northern sky and that the North Star is at its center; also imagine that the circle passes through the Big Dipper Look on the opposite side of the circle and you will find the pretty group called Cassiopeia. It looks like a chair.

Probably our most beautiful group of constellations is the one seen in the east in the early evening during November and December. It is made up of the Pleiades, a brilliant cluster, followed by the red star, Aldebaran, in the eye of Taurus, the Bull. Behind these and a little farther south is Orion, with his belt of three bright stars and his sword of three fainter ones. After Orion comes the Great Dog (Canis Major) with the Dog Star, Sirius. This is the brightest fixed star of the sky.

The Galaxy, or Milky Way, is a belt of light which passes across the heavens. The telescope shows us that it is made up almost entirely of separate stars, each too small to be seen by the eye

alone. 88. How Far Away are the Stars ? — The brightness of the stars depends upon how much light they give off ar also upon how far away from us they are.

The star Sirius gives off 40 times as much light as our sun, but it is enormously farther away. For distances on the earth,

a

a

the mile (5280 feet) is the unit, but how little we are able to understand the distance to the sun, when some one says that it is about 93,000,000 miles away! A train traveling a mile a minute would need about 178 years to go from the earth to the sun. Light travels about 186,000 miles a second, yet even light requires 499 seconds (over 8 minutes) to reach us from the sun.

If we think the sun is far away, then what shall we say of the distance to the nearest fixed star, the light of which requires between three and four years to reach us? Can you realize the distance to the North Star when you are told that the light that comes to our eye tonight left the star at least 47 years ago?

89. Why are Some Heavenly Bodies Wanderers ? As we have learned, the stars in a constellation hold their places, but the constellations themselves seem to move around the sky from east to west once each day. They seem to do this because the earth rotates from west to east. There is another important change in the constellations. If we watch one of them, such as the Pleiades, from month to month, we shall see that it rises earlier and earlier each evening; until at the end of six months, instead of rising in the east at sunset it now rises and sets with the sun. Then we cannot see it at all, because the sun makes a much brighter light. After six months the constellation again rises at sunset. Another way of saying this is that the sun is a “wanderer " and moves eastward among the stars. First it is in one constellation, then in another farther east, until it has gone entirely around the heavens in a great circle.

a

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Fig. 57, a and b. Fold the inner margin of the page so that the halves hold the map so that the North Star of the map is directed toward the North of the map; the stars will then appear somewhat as they should be at about from the pole. (Suggested by Young's Astronomy.)

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of the map come together. Grasp the book with both hands, face north and Star of the sky. Turn the map so that the present month shall be at the top

The map shows some of the constellations that are less than 50 degrees

8 P.M.

10

If you look at an almanac, you will see the list of “ Signs of the Zodiac.” The zodiac is made up of the twelve constellations through which the sun seems to move; they were used by the ancients to tell seasons.

Why does the sun seem to make a journey around the sky every year? The answer is that this apparent moving of the sun is due to the revolution of the earth around the sun every twelve months. So we must get used to two apparent motions in the sky, both of them due to the motions of the earth itself: (1) the change from sunrise to sunset and from sunset to sunrise, caused by the fact that we are being carried around once each day by the rotation of the earth; (2) the yearly changes in the sky, caused by the fact that we are being swept around the sun and back to the place of starting, in one year. You have all had the strange experience of imagining that the train on which you were riding was standing still, while barns, trees, and people were dashing madly by. That is the kind of experience we have all our lives, unless we think out what is really happening.

Besides the sun and the moon, there are several other heavenly bodies which do not remain in any constellation as the fixed stars do; these are the planets, or wandering stars. They appear to move irregularly among the stars because they really revolve about the sun, just as our earth revolves around it. When they seem to be in a certain constellation, it is because they are between the earth and that constellation.

90. What is the Sun Like? The sun is a star. While it seems to us to be very large, we know that there

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