AS讲TRONOMY130讲述.docVIP

ASTRONOMY 130 CONSTELLATION STUDY - WINTER SKY PURPOSE: To be able to identify stars in the sky for the particular season of the year. PROCEDURE: The stars and constellations will first be observed in the planetarium and then in the actual sky. CONSTELLATION SYSTEM: The Greeks recognized the impossibility of attempting to learn much about the heavens without first organizing their information about the vast number of stars in some systematic system. The geometric arrangement of some stars provided the Greeks with a natural organizational system which we call constellations. By connecting the stars with imaginary lines, the ancients saw pictures in the sky. These constellations have names and a star may be identified as being in a certain constellation. Although the modern astronomer no longer employs these constellations as the ancients did for mythological or astrological purposes, he does use them for quick reference purposes. Originally, the constellations did not encompass all of the stars, but in 1933 the International Astronomical Union divided the entire celestial sphere into 88 constellations using regular north-south or east-west boundaries so that all stars (and areas of the sky) are now assigned to a constellation. Almost everyone is familiar with a few constellations, such as Ursa Major, Orion, and Scorpio. One could identify the star Alkaid as being the end star in the tail of the constellation called URSA MAJOR. See Figure 1. GEOMETRIC DESIGN OR ASTERISM SYSTEM: In the geometric design system we again connect stars by imaginary lines. Since this system originated after the constellations were established the geometric designs (asterisms) do not carry the prestige of the constellations. Nevertheless, they are easily identifiable and quite useful. They sometimes are comprised of only part of the stars of a constellation or some stars from two or more constellations. For example, the three stars Vega, Deneb, and Altair form the geometric design of a