In astrology, the royal stars of Persia are Aldebaran, Regulus, Antares and Fomalhaut. They were regarded as the guardians of the sky during the time of the Persian Empire (550 BCE–330 BCE) in the area of modern-day Iran. The Persians believed that the sky was divided into four districts with each district being guarded by one of the four Royal Stars. The stars were believed to hold both good and evil power and the Persians looked upon them for guidance in scientific calculations of the sky, such as the calendar and lunar/solar cycles, and for predictions.
The royal stars are mentioned in the Bundahishn, a collection of Zoroastrian cosmogony and cosmology.
The four stars with their modern names and their ancient Persian names (in brackets) were:
Note that the watchers of each direction have also been associated with other stars/constellations. Some references have swapped Satevis to Antares, and Hashtorang to Fomalhaut.These associations, however, are thought to be modern inventions, and furthermoreTascheter has been associated with Sirius and Haftorang with Ursa Major.
In 747 BCE the Babylonian King Nabu-nasir adopted a calendar derived from the motions of the moon relative to these four stars, one following an eight-year cycle, and one a nineteen-year cycle (later adopting the nineteen-year calendar as standard).
By 700 BCE the Assyrians had essentially mapped the ecliptic cycle and used the positions of these four stars to identify the zodiacal constellations, distinguishing the fixed stars from the planets.
By the time of the Persian Empire (550 BCE–330 BCE), Aldebaran watched the Eastern sky and was the dominant star in the Taurus constellation, Regulus watched the North and was the dominant star in the Leo constellation, Antares watched the West and was the alpha star in Scorpio, and Fomalhaut watched the Southern sky and was the brightest star in Piscis Austrinus (sharing the same longitude with the star Sadalmelik which is the predominant star in Aquarius).
Aldebaran marked the vernal equinox and Antares marked the autumnal equinox, while Regulus marked the Summer Solstice and Fomalhaut the Winter Solstice. While watching the sky, the dominant star would appear in its season, each having a time of the year when most noticeable. Regulus was seen as the main star because it was in the constellation of Leo, giving it the power of the lion, signifying the strength of kings with large implications.
The constellations of the royal stars were said to be fixed because their positions were close to the four fixed points of the sun's path. The sun was then surrounded by four bright stars at the beginning of every season. From this observation individuals began to denote them the royal stars.
The royal stars were used primarily for navigation. They were also believed to govern events in the world. Major disasters, breakthroughs, and historical phenomena were seen as caused by the stars and their alignment in the sky during the time in which the event occurred. When the stars were aligned accordingly, favourable conditions followed, and when they were negatively aligned, disaster was predicted. Because Regulus was the most influential of the royal stars, events that took place while Regulus was in dominance were amplified and grave, foreshadowing destruction, depending on what planet or planets might be in conjunction with the star.
The "Four Royal Stars of Persia" were addressed conceptually in a volume of "Popular Astronomy", published in 1945 and authored by George A. Davis Jr. Davis was critical of the often quoted connection between the modern concept of the royal stars and ancient Persia. He did not fully dismiss the usage of the stars - or the respective constellations they belonged to - as was proposed to establish the four cardinal directions of the celestial sphere and/or for the demarcation of equinoxes and solstices. However, Davis clarified information regarding the Zoroastrian mythos and celestial naming-scheme employed within the Vendidad, pointing out that the Persian names referred to either different stars or constellations than the stars commonly identified as the royal stars. Davis also dismissed the proposition that the stars/constellations had been used circa 3000 BC (in the case of the Persians) and pushed the date up to, at the earliest, 650 BC when written Persian history began.