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The 88 groups of stars, known as constellations, are officially recognized and defined by the International Astronomical Union (IAU). Here are some key points about these constellations:

Definition and Boundaries

Each constellation is a region of the sky bordered by arcs of right ascension and declination, together covering the entire celestial sphere. The boundaries for these constellations were officially adopted by the IAU in 1928 and published in 1930[2][4].

Historical Origins

Many of the constellations have their roots in ancient cultures, particularly the ancient Mesopotamians, Greeks, and Romans. The Greek astronomer Ptolemy listed 48 constellations in his 2nd-century work, the Almagest, which formed the basis for many of the constellations recognized today. Later, European astronomers added more constellations to fill gaps and to map the southern skies[1][2][4].

Categories and Representations

The 88 constellations depict a variety of themes:

42 animals
29 inanimate objects
17 humans or mythological characters[3].

Zodiac Constellations

Twelve of these constellations are part of the zodiac, which lie along the Sun’s apparent path in the sky, known as the ecliptic. These include constellations like Leo, Virgo, Scorpio, and Pisces[1][3][4].

Modern Standardization

The IAU standardized the 88 constellations to ensure that every point in the sky belongs to one constellation. This standardization included dividing some of the older constellations into new ones. For example, the ancient constellation Argo Navis was divided into Carina, Puppis, and Vela[2][4].

Observability

While the stars within a constellation may not be physically close to each other, they form recognizable patterns that help people orient themselves in the night sky. Not all stars are part of the visible patterns, but all stars fall within the boundaries of one of the 88 constellation regions[4][5].

Unique Features

Each constellation has its own unique features, such as notable stars, deep-sky objects, and historical significance. For instance, the constellation Hydra is the largest, covering 3.2% of the southern night sky, while others like Orion and Scorpius are easily recognizable due to their bright and distinctive patterns[1][3][4].