If you were asked how many stars can be seen any clear night in the sky, you would very likely say--“Oh, thousands and thousands!” You might even reply, “Millions!” But nobody ever yet saw a million stars without the help of a telescope. Commonly we see at most only two or three thousand stars; and not often so many at once. For convenience the stars are arranged in Classes, first, second, third, and so on, like the classes in a school. These Classes are spoken of as Magnitudes, which means “Sizes.” But the stars really are put into Classes according to their _brightnesses_: not according to their sizes. We know very little as yet about the true sizes of the stars. They all look to us, in even the biggest telescopes, as mere bright points, showing no size at all. Some of the brighter stars may be much smaller than others which seem to us more dim. The shining of a star in our sky depends upon two things. It depends partly on the size and brightness of the star. It depends partly on the nearness of that star to the Earth. All we are able to do is to arrange them in classes according to their _brightness_ as seen from the Earth. Those which shine the most are called Stars of the First Magnitude; those which come next in brightness are called Stars of the Second Magnitude; and so on. In the whole sky all around the Earth there are only about twenty Stars of the First Magnitude. Those twenty stars are mere bright points in the sky; none of them so bright as Venus and Jupiter look to us. Yet they are all Suns; radiant globes of heat and light more or less like our own great Sun; not like a mere planet. QUESTIONS. 1. What is meant by the Stellar System? The Universe of Stars to which our Sun belongs. 2. How are Planets known from Stars? The Stars remain fixed in groups, while Planets are always changing their places among the Stars. 3. What is meant by “Fixed Stars?” The Stars are so called because of their fixity in certain groups. 4. Tell me the name commonly given to groups of Stars. They are called Constellations. 5. Name two or three Constellations mentioned in this chapter. The Little Bear; the Great Bear; Orion. 6. Are the Stars really fixed? No; they are believed to be all moving. 7. If the Stars are moving why do we not see it? Because of their immense distance from us. Our lives are not long enough for us to see most of the Stars change their places in our sky. 8. Is the Sun at rest? Our Sun journeys like other stars through the sky. 9. Does he ever leave his planets behind? No; he carries them all with him. 10. How does he do so? By means of his powerful attraction. 11. What is the meaning of “Magnitude?” The word “Magnitude” means “Size.” 12. What is meant by Star-Magnitudes? The Stars are divided into different classes, called Magnitudes--such as Stars of the First Magnitude, Stars of the Second Magnitude. 13. Are all Stars of the First Magnitude larger than all other Stars?