Finding Figures in the Sky

Astronomers in times past noticed that the entire body of stars appeared to be moving in an orderly way. Although stars passed along the sky from east to west, they did not change their positions in relation to one another.a In other words, each night the same specific groupings of stars were visible. Since man wanted to bring some order to those countless points of light, he connected stars into groups. With a little imagination, these groups resembled animals, people, or inanimate objects. In this way the practice of regarding set configurations of stars as constellations came about.

Some of the constellations we know today were first described in ancient Babylon. Among these are the 12 constellations representing the signs of the zodiac. These played—and still play—an important role in astrology, the divination of the supposed influence of the stars on human affairs. Looking for omens in the stars, though, is condemned in the Bible. (Deuteronomy 18:10-12) Yet, worshipers of Jehovah God were aware of the existence of constellations. The Bible book of Job, for instance, speaks about Jehovah as the one “making the Ash constellation, the Kesil constellation, and the Kimah constellation.”—Job 9:9.

The names of many of the constellations that we know today are from Greek mythology. Names like Cepheus, Cassiopeia, Andromeda, and Hercules can still be found on modern-day star charts.

Star Charts From the Past

About 150 C.E., the Greek astronomer Ptolemy produced a summary of the astronomical knowledge of his time. This summary, entitled Almagest, contains a list of 48 constellations. Charts and atlases of the sky that were made in the centuries after Ptolemy usually featured the same 48 constellations. In fact, until about the 16th century, the number of constellations did not change.b Later, 40 other constellations were added. In 1922 the International Astronomical Union officially adopted the list of these 88 constellations.

Besides constellations, Ptolemy’s publication includes a list of more than a thousand stars, with information about their brightness and their position in the sky. Not only does Ptolemy give the position of a star in celestial longitude and latitude but he adds more detail. For instance, one star in the Ursa Major, or Great Bear, constellation is described as “the star at the beginning of the tail,” and the location of a comet is given as “to the left of Andromeda’s right knee.” Thus, “every good astronomer,” notes one textbook, “had to know his celestial anatomy!”

Why, though, are most ancient constellations located in the northern sky? That is because the practice of regarding certain groups of stars as constellations originated in the Mediterranean area, where the northern sky is visible, explains a uranographer, or cartographer of the sky. Only later, when man began to explore the southern sky, were new constellations identified. Some of these newer constellations have names such as Chemical Furnace, Pendulum Clock, Microscope, and Telescope.