=The Milky Way.=—You have, no doubt, often seen on a clear, dark night, a wide, ragged band of light stretching from the northern sky across the celestial equator and beyond. This band of light is the famous Milky Way. If, as you were looking at the Milky Way, the Earth could be moved from under you and you were left standing in space alone so that you could see in every direction, you would find that the band formed a complete ring round the sky. To the naked eye the Milky Way seems to be made up of mists of matter as thin as the stuff of which comets’ tails are made. There are some patches, though, that are very bright, but look at them as long as you will with the naked eye nothing more can be seen than just a milky patch of hazy white, as shown in Fig. 133. With a very small telescope, however, this band of luminous matter will be instantly changed into thousands of stars, all separate and distinct, and some of these stars will look about as large as the stars of the Pleiades when these are seen with the naked eye, while others will shine as brightly as Venus or Jupiter when they are nearest to the Earth. These bright patches, then, which form the Milky Way, are really groups of stars or star-clusters, and when some of these clusters are photographed through a telescope as many as 15 or 20 thousand stars can be counted, while the real number of stars that lie beyond and which cannot be seen is past all calculation, and, just think of it, every one of these stars is a Sun as large or larger than our Sun! Those who have made a deep study of starcraft tell us that our Sun is one of the stars of the Milky Way, and since the other fixed star that is nearest to us, which is _Alpha Centauri_, is 25 trillion miles away, and Sirius, the Dog Star, which is the brightest star in the whole sky, is three times as far away as Alpha Centauri, we may gain some slight idea of the enormous distances of the fainter stars that make up the Milky Way. =The Nebulæ.=—Unlike the bright, cloud-like patches in the Milky Way, and which the telescope shows to be formed of separate and distinct stars, are the faint misty spots in the sky called _nebulæ_ (or nebule). Now the nebulæ give us a clew as to how the stars were made, and how other stars are now being made, for it is believed that the nebulæ are the raw material which, when set in motion, produced heat and took on form and became Suns and planets like our own solar system. The nebulæ are formed of luminous gas. Some of them are great irregular clouds of gas, many are more or less spiral in form, others are condensed so they look like fuzzy stars.