Navigatio Part V

Have you looked at all at the family of the stars? --- Paul Kantner


As of 2018, astronomers recognize 88 constellations in Earth's night sky, either named by the ancients or catalogued by Ptolemy the Librarian of Alexandria, or others created afterward, mostly during the Age of Discovery. The asterisms formed by the stars were critical to maritime navigation, and have special mention in the Nautical Almanac.

Until 1928, constellations were simply the most important asterisms in the sky (asterisms are stars that form apparent patterns). Prior to 1928, whether a star belonged to a constellation was largely a matter of opinion --- Did it form the lines of the stick figure that made up the constellation? Was it within the lines of the stick figure? If it was outside the lines, was it reasonably close to the stick figure? Was it bright? Was it an important star? Such stars were included in the constellations. Dim, outlying, and hence unimportant stars were left homeless. 

To force-fit certain stars into certain constellations, celestial mapmakers, who were called uranologists and were usually artists, drew complicated figurines in the sky, and "connected the dots" as it were in very different ways. The asterism of the Great Square of Pegasus, for example, either represented the flying horse's body or his wing, depending on who was doing the imagining. And of course, different cultures perceived the constellations differently, especially the less important constellations.What was a scorpion in Babylon was a fishhook in Hawai'i.

Over time, some astronomers invented new constellations to honor their nation, their patron,or their prince. Some constellations that once existed have been abolished by fiat or  practice. An example is Cancer Minor, an unsuccessful asterism created just because neighboring Leo has a "Minor." However, no one seemed to take a liking to the Little Crab, and it vanished from the star charts. 

To call the mapping of the heavens an unscientific system was just to state the obvious. As astronomy began formalizing itself in the 20th Century the members of its governing body, the International Astronomical Union (IAU) decided to set boundaries for each constellation. Like a World Map divided into so many nations the Sky Map was divided into so many constellations, and every star within a boundary line now belongs to that constellation whether it forms the asterism of the constellation or not. 

It still is not a perfect system, especially in places where the constellations crowd each other. Some stars that form the asterisms of their constellations overlap into an adjoining constellation or are shared between them. Thus, the shared stars may have multiple designations --- and there are already numerous conventions for star names, such as a star's Bayer Designation (proper name), its Flamsteed Designation (a numerical listing), its Gould Designation (if it is in the Southern Hemisphere), its Hevelius Number, its Bode Number, and its ranking in the Bright Star Catalogue. There has also been some objection to the exclusive use of Eurocentric names, as the Chinese, the Native Americans, the Australian Aborigines, and the peoples of sub-Saharan Africa and Oceania all have their own cultural constellations. 

Currently, the 88 constellations are grouped into two categories, 48 Classical and 40 Modern, divided into eight Families: 

The La Caille Family (Modern) was formalized in 1756 by Nicholas La Caille, a French astronomer who named a series of thirteen small, dim and far southern constellations for a series of scientific instruments. When La Caille introduced these constellations he was met with some derision: "It sounds like a toolshed!" the Astronomer Royal of Britain was said to have remarked. Nevertheless, most of La Caille's constellations were accepted by the scientific community. 

The Bayer Family (Modern) was formalized in 1603 by Johann Bayer of Germany, who introduced eleven dim, southern constellations, including the Sub-Family of the Southern Birds, created during the late Age of Discovery. Some of Bayer's constellations are based on the asterisms recognized by the local peoples. 

The Celestial Sea (Classical) dates back as far as the Sumerians. All nine constellations in the Celestial Sea are either sea creatures or have reference to water. 

The Orion Family (Classical) includes Orion and his two hunting dogs the Greater and the Lesser, Lepus The Rabbit, and Monoceros The Unicorn. 

The Perseus Family (Classical) is made up of nine constellations, almost all relating to the Greek myths surrounding the hero Perseus. 

The Ursa Major Family (Classical) are the ten constellations which are circumpolar and revolve around Polaris. For the most part they do not set in the Northern Hemisphere. 

The Hercules Family (Classical) consists of 19 diverse constellations that cover 130 degrees of the Western Celestial Hemisphere, the largest single region of the sky. This Family formally includes Ophiuchus The Snake Handler who some astronomers (and astrologers) assign to the Zodiac. 

The Zodiac (Classical) or "Circle of Animals" may be the most ancient, and is certainly the best well-known of the eight Families. The Sun and the planets appear to be moving through the constellations / signs of the Zodiac, and this movement is the basis of the ancient science and art of astrology.

The 88 constellations shown in a Mercator-type Projection. The rectangles represent the borders of the constellations. The "connect the dots" lines show the major asterism of each constellation. The central wavy line is the ecliptic, the Sun's path through the sky; the central straight line is the celestial equator; and the blue u-shaped line is the galactic plane along which lies the Milky Way.