Astrology, Power and the Roman World

In the Roman Empire, knowledge of the stars could get you killed—or help you kill others. Discover how the science of reading the heavens became a powerful political tool in the Roman world.

Published Categorized as History
AV Aureus (7.74 g, 6h). Pergamum mint. Struck 19 BC. AVGVSTVS, bare head right; SIGNIS above, RECEPTIS below, capricorn right. Classical Numismatic Group, Inc.
Capricorn – The Sun sign of Caesar Augustus (63 BC - AD 14)

In the early years of the Roman Empire astrology was held in high regard. It was seen as a legitimate way of predicting the future of individuals, including the powerful, such as the Roman emperors. As an art and a science, astrology had an intricate philosophy and complex techniques that allowed the astrologer to uncover the path of someone’s life, their motivations, their career, love life, and even the length of their life and time of their death.

Furthermore, the popularity of astrology made it an important asset for emperors and politicians. It had an impact on popular opinion, as people were familiar with the symbols of the zodiac and the planets. As the practice of astrology allowed the understanding of one’s future and that of others, emperors made use of it to better govern according to their interests. In this article, we will touch upon the relationship between astrology and power in the Roman Empire, and how astrology was viewed as a legitimate and politically valuable practice.

Caesar Augustus and Capricorn

Augustus was the first Roman emperor, ascending in the chaos that marked the end of the Roman Republic. His rise came at a time of great change, as the entire Roman government came under the control of a single individual. With that, Augustus not only ascended to power but also popularized himself as a divine being of the uttermost importance, above regular humans.

One resource that he made use of to increase his popularity was astrology. On one hand, it was widely recognized popular knowledge; on the other, its predictions about the fate of all were seen as reliable. Augustus published his own natal chart as a way to demonstrate to the public that he was destined to rule.

Another association that he made use of was the sign of Capricorn, which he claimed as his own Sun sign and whose symbol he put on official coins. The symbolism of this move was significant: in the Northern Hemisphere, when the Sun is in Capricorn, the day starts to grow in length once again following the Winter Solstice, the shortest day of the year. In this sense, Augustus’ association with Capricorn was an approximation with the glory of the Sun recovering its power, indicating that, after all the civil wars that preceded him, there was finally time for peace.

Astrologers in the Imperial Court: Thrasyllus

The successor of Augustus was Tiberius. He had been in exile on Rhodes, an island in the Aegean Sea, before he became emperor. There, according to legend, he had a consultation with the astrologer Thrasyllus, who visited him in his house. He was impressed with the knowledge of this astrologer, who said that he would succeed Augustus as the next emperor. Tiberius, however, had a tyrannical habit after consultations: he would throw the astrologer off the cliff his house was on.

Half-length portrait of Tiberius emperor of Rome, from behind, facing towards the right, surrounded by an etched frame with swept centres and corners
Tiberius, emperor of Rome

So, after the Thrasyllus made such an auspicious prediction about him, he decided to test the astrologer: he asked what Thrasyllus predicted for himself in that very moment. After some quick calculations, the astrologer became terrified and said that he was in imminent fatal danger.

Impressed, Tiberius decided that, instead of throwing him off a cliff, he should make Thrasyllus his official astrologer when he became emperor. Thus, Thrasyllus became the first known court astrologer in the Roman Empire.

This unprecedented post brought rewards and recognition to Thrasyllus. Unfortunately, his works have not survived to the present day, but we know that he wrote a treatise named Pinax in which he mentions Nechepso, Petosiris, and Hermes, three of the mythic founders of astrology.

An astrologer being such an important consultant for the emperor indicates the importance given to astrology in the Roman Empire. Through the information provided by it, Tiberius could make better decisions on topics such as war and politics, and even persecute opponents according to their natal charts.

Tamsyn Barton, in her book Ancient Astrology, mentions that Thrasyllus saved the life of many by assuring Tiberius that he had many years of life left. This was necessary because the discovery of natal charts indicative of power could lead to the execution of the owner of that chart, eliminating the risk of him becoming emperor by murdering the current one.

Court Astrologer to three Emperors: Balbillus

Another famous astrologer from the early years of the Roman Empire was Balbillus. Some authors, including Chris Brennan, believe that he was the son of Thrasyllus, which indicates some sort of astrological lineage.

Balbillus was the court astrologer for Claudius, Nero and Vespasian. Besides being an advisor for the most powerful figures of the empire, Balbillus also held important offices in Egypt, where he was born. According to Brennan, he was the high priest of the temple of Hermes in Alexandria, overseer of all imperial buildings and sacred sites in Egypt, and the head of the Museum and Library of Alexandria.

After his death, a festival called the Balbillea was held in the city of Ephesus to pay homage to him. These festivals were maintained from the year 85 A.D. until the mid-third century.

Just like during the reign of Tiberius, astrology in Balbillus’ time could also lead to the death of people. Barton mentions that, when Nero was in power, Balbillus recommended the infamously blood-thirsty emperor kill various senators to avoid the risks imposed by the passage of an ominous comet. This advice was quite the opposite of the kind that Thrasyllus gave to appease the fears of Tiberius; the researcher Benson Bobrick even says that Balbillus, under the reign of Nero, showed himself to be a man of unquenchable malice, as he was responsible for the death of many.

Astrology in honorable positions

The powerful positions given to Thrasyllus and Balbillus, alongside the importance given to astrology by Augustus, demonstrate the value placed on this knowledge in the Roman Empire. Astrology was held in high regard, at least in the sense that the knowledge of the stars and the fates that they decreed was potentially powerful and, for this reason, dangerous.

We can suppose that part of the reason for Tiberius to murder astrologers that came to him was a way of keeping them from using their predictions for conspiracy or personal gain. On the other hand, as Bobrick suggests, he could have been reassuring himself of the quality of their predictions: after all, if they could not predict their own death, how could they reliably predict anything? With this, he could be sure as well that the astrologers were not just flattering him.

However, this cruel measure inflicted on astrologers was in no way indicative of disdain for astrology. There was nothing seen as superstitious in how powerful emperors dealt with astrologers, who functioned as valuable advisors. It is different from what we see in the relationship between Ronald Reagan and astrology, as Barton points out. In Roman times, astrology was understood as a legitimate way of knowing the truth of the cosmos and discovering the fate of  individuals.

For that same reason, practicing astrology was not always a bed of roses: astrologers were frequently at risk of imprisonment, banishment, and execution.

Astrologers in danger

In the year 139 B.C., according to the Roman historian Valerius Maximus, astrologers and worshipers of Zeus Sabazios were banished from Rome and Roman Italy.

A century and a half later, when Augustus reached old age, in 11 A.D., he forbade private astrological consultations, especially about someone’s death. This was possibly a way of preventing the prediction of his own death or, worse still, the hatching of an astrologically backed conspiracy to kill him for his power.

Contemporary to Tiberius, a man named Marcus Scribonius Libo Drusus was accused of consulting astrologers, magicians, and dream interpreters, and of hiring one of them to use magic against the imperial family and senators. He was accused of planning a coup and committed suicide before the trial. Astrology was being used in conspiracies, and right after the accusation of Libo, the Roman Senate passed a decreed against astrologers and diviners, even executing two men because of it.

Other similar events occurred throughout the history of the Roman Empire. The capacity to uncover the future, including the fate of emperors, would make astrologers not only powerful but dangerous. For this reason, politicians found it necessary to regulate their power.

On one hand, we have Thrasyllus, a celebrated and honored astrologer guiding the emperor Tiberius; on the other, we have people like Libo and his astrologers, who were persecuted and executed for practicing the same art. The relationship between Roman emperors and astrological art was directly related to the kind of things that astrologers could know.

The use that Augustus made of astrology to highlight his natal chart as proof of his right to rule was similar to the later practice of executing political rivals due to features of their own charts that identified them as risks to the emperor’s power. The presence of astrologers in court was important for the same reason that private astrologers predicting the death of emperors was dangerous and forbidden. Astrology was knowledge, and knowledge is power.

Not surprisingly, we find an important astrologer of the 4th century, Firmicus Maternus, asserting in his book, the Mathesis, that no astrologer could ever predict the future of the emperor. Firmicus depicted the emperor as above the power of the planets and closer to God. As so, he advises astrologers not to try to make this kind of prediction and not to accept clients that want it. By putting the emperor above the stars, Firmicus was probably trying to mitigate the risk of persecution upon him and even his eventual readers – after all, Firmicus was a senator. If there was any suspicion that he was making predictions about the life of the emperor, he would certainly have been severely punished.

Today we live in a very different world, and it is fascinating to imagine a time when astrology was taken so seriously that wars were begun, and people were executed based on the path of the stars. Even if some politicians today may be interested in astrological advice, the general sense is that nobody should rely too heavily on it. As we saw, the case was radically different in the Roman Empire.


  • BARTON, Tamsyn. Ancient Astrology.
  • BOBRICK, Benson. The Fated Sky: Astrology in History.
  • BRENNAN, Chris. Hellenistic Astrology.
  • Thrasyllus at
  • WHITFIELD, Peter. Astrology: A History.

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