1. How People Imagined Shapes in the Stars
People have long looked at the arrangement of stars in the night sky and imagined them as animals or tools, giving them names. The National Astronomical Observatory of Japan explains that people have connected stars in this way since ancient times. [2] No single group of people imagined all the patterns. According to the Astronomy Dictionary, while the origins of constellations are often traced to ancient Mesopotamian civilization, various civilizations created their own constellations at different times. [1]
It is similar to looking at clouds and saying, "That looks like soft-serve ice cream." Different people see different things in the same cloud. However, clouds change shape quickly, while the arrangement of stars looks almost the same even after thousands of years. Because the arrangement of stars looks almost the same, generations of people could pass down the same imaginative shapes to one another.
2. The Oldest Star Shapes: Mesopotamian Stars on Clay and Stone
The oldest evidence that clearly shows people were imagining shapes in the stars comes from Mesopotamia around 3000 BC, where stars were carved into stone or clay tablets. [6] This was about 5,000 years ago. There is a theory that cave paintings from the Paleolithic era depict constellations, but this is not widely accepted by scientists. [6]
From around the 12th century BC, Babylonian texts known as "Three Stars Each" lists began to appear. These lists arranged stars in groups of three. Around 1000 BC, this information was compiled into a document called MUL.APIN, which contains many stars and constellations. [7] This shows that people did not just look at the stars; they recorded star lists on clay tablets to pass the information on to the next generation.
3. How Babylonian Zodiac Signs and Greek Myths Shaped Constellations
Around the 5th century BC, Babylonian astronomical texts began to describe the positions of the Sun, Moon, and planets using 12 equal divisions called signs. Constellations near the ecliptic were linked to these signs. This system later became a set of 12 signs and was adopted in Egypt and Greece. [7]
Around the 4th century BC, Babylonian star lists entered Greek astronomy through figures like Eudoxus. The constellations of Scorpius, Leo, and Taurus come from the Babylonian "Scorpion," "Lion," and "Heavenly Bull." [7] As Mesopotamian constellations spread to ancient Greece, poets linked them with myths and legends. [5] Many of the stories we remember alongside constellation names were added during this stage.
4. Ptolemy’s List of 48 Constellations and the Southern Sky
Around the 2nd century AD, the Greek astronomer Ptolemy organized the constellations known up to that time into 48, which are almost the same as the ones we know today. This system was used for about 1,500 years. [5] His book, the Almagest, contains a star catalog listing 1,022 stars divided into these 48 constellations. Some of this catalog can be traced back to the earlier astronomer Hipparchus. [8]
According to the Astronomy Dictionary, constellations in the northern sky originated in ancient Greece, while those in the southern sky were created during the Age of Discovery from the 16th century onward. [1] It is reported that Lacaille added 14 southern constellations in 1752. [6]
5. How the IAU Defined the 88 Constellation Regions
The names and number of constellations varied by era and country. In 1922, at the first general assembly of the International Astronomical Union (IAU) held in Rome, a committee agreed on the names and abbreviations for 88 constellations. [3]
Even after the names were decided, the borders between constellations remained vague. A Belgian astronomer named Delporte proposed borders along lines of right ascension and declination. This was discussed at the 1925 assembly, adopted at the 1928 assembly in Leiden, and published in 1930 as "Delimitation Scientifique des Constellations." [2][3] Because of these borders, every star in the sky now belongs to exactly one constellation.
6. What It Means When an Object Is “in” a Constellation
When astronomers say, "This object is in Orion," they do not mean it is part of the star pattern. They mean it is inside the defined border of the Orion region. [3] This is similar to saying a town is "in Yamanashi Prefecture." It means the town is inside the prefectural border, not that it is part of the shape of the prefecture. However, there are no visible markers for these borders in the night sky. The borders are invisible lines defined by coordinates of right ascension and declination.
While names and borders are standardized, there are no official rules for how to connect the stars or how to draw the pictures. [4] So, to answer the question from the beginning: the lines were not officially drawn by anyone. People have connected stars in different ways throughout history.
7. Try Drawing Your Own Constellation from Random Dots
If you want to try this yourself, put about six random dots on a piece of paper. Connect them with lines and give the shape a name. It is interesting to show it to a friend and ask if they see the same shape. Since there is no official way to connect the stars, there is no right or wrong answer.
If you want to learn more, Japan has its own star names. "Subaru" is said to come from the word "sumaru," which evokes beads on a necklace. Later, the character 昴 was borrowed from the Chinese lunar mansion 昴宿. The Pillow Book also mentions, "Stars are Subaru." [9] You can read about this in the Rare Materials Exhibition Room of the National Astronomical Observatory of Japan. When going outside to see stars at night, go with an adult and watch your step.