Stars in the Night Sky
For years humans have traced patterns in the night sky, these patterns are called constellations. Constellations aren't real in fact they are imaginary things that poets, farmers, and astronomers have made up. The real purpose of constellations is to help us tell which stars are which. To most people a constellation is a group of bright stars, but to an astronomer it is a definite area in the sky (Motz). Thus every star, no matter how dim, lies in one constellation or another, just as any point in the world is in one country. Although all the stars in the same constellation look close together in the sky, they are not necessarily close in space because some may be much farther out in space than others.
The boundaries of the constellations used to be very irregular and had many curved lines. In 1928 astronomers straightened them out so that the outline of any constellation includes only straight lines running north and south or east and west.
Astronomers use the constellation names to identify most bright stars and all variable stars, so it was important to make the boundaries clear and precise . They divide the celestial sphere into 88 constellations, 47 of which date from ancient times and were listed by the astronomer Ptolemy (Motz). The boundaries are often complex, but all segments of the constellations lie east to west and north to south on the celestial sphere.
The zodiac, widely used in astrology, consists of 12 constellations through which the orbital motion. The suns yearly path is called the ecliptic. The times when given constellations rise and set depends on the time of year and on the observers position on the earth's surface. Constellations also slowly shift on the celestial spheres coordinates...