Galaxy

Galaxy, or Milky Way, is a luminous belt of stars, nearly surrounding the heavens in a complete circle. It is in one thick band for about two-thirds of its length, but for the remainder it is divided into two parallel strips. It intersects the ecliptic near the solstices at about an angle of 60°. It is composed almost entirely of small stars of the eighth and higher magnitudes. In it are a great number of star clusters, but not many true nebulae. Certain parts are so thick with stars that they cannot be counted. The two Herschels made careful estimates of the number of stars in various parts of the galaxy and of other regions of the heavens, but by reason of unfounded assumptions concerning the size and distance of the stars they arrived at incorrect conclusions as to the structure of the heavens. It is now generally understood that the great mass of stars in our stellar system lie in or near a plane passing through the Milky Way; they are contained, in fact, in a disc-shaped region, whose diameter is about ten times its thickness. They are not arranged with anything like uniform distribution, but in irregular clusters. Our own sun is a member of the system, and occupies a position near the centre of this region. The rest of the heavens on each side of the Milky Way is comparatively starless, but contains a large number of nebulae.