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Warhammer 40K: What Is The Astronomican Anyway?

6 Minute Read
Jun 4 2022

The Astronomican is the Emperor’s great beacon. Without which warp travel would be impossible. But watches the astronomical lighthouse?

The Astronomican

The Astronomican is a psychic beacon which the Navigators use to pilot the spaceships of the Imperium through the otherwise unnavigable chaos of Warp-space. As the beam generated is psychic, it exists within the psychic universe of the Warp. It is the duty of the Adeptus Astronomica to maintain all aspects of the Astronomican, including training those who will power it.

The Astronomican was originally constructed in M30 in preparation for the Great Crusade. The Emperor brought in large numbers of Tech-Priests and drafted much of Terra‘s population for the gargantuan task of constructing the Chamber of the Astronomican at the Forbidden Fortress. At the time of its construction, the Astronomican was the single largest structure on Terra, though this would later be surpassed by the Imperial Palace. In the days of the Great Crusade, the Astronomican was powered by the Emperor’s own psychic might directly. Without the beacon of the Astronomican to guide their ships through the Warp, Imperial armies would not have been to have waged the Great Crusade.

After the Heresy, the Emperor became interred within the Golden Throne and required increasing numbers of Psyker sacrifices to maintain the Astronomican. Today, the Astronomican is powered by ten thousand psykers trained by the Adeptus Astronomica. The omnipotent will of the Emperor constantly directs this energy across around fifty thousand light-years of the galaxy. Although the Emperor does not provide the energy of the beacon, only he has the psychic power to handle such immense energy and direct it across the galaxy.

The psykers who power the Astronomican are recruited into the organization through the Adeptus Astra Telepathica. They are initiated into the Adeptus Astronomica as Acolytes and taught how to use their powers, philosophy, the meaning of their lives, and the Lore of the Astronomican. Some achieve a mystic state, gaining the status of Chosen. It is these Chosen who are eventually called to serve in the Chamber of the Astronomican. Here they fuel the Astronomican beacon with their psychic energies; as their powers are drained the Chosen slowly fade and die. Up to one hundred Psykers die each day powering the Astronomican.

However, the psychic power they generate through their sacrifice is directed by the mind of the Emperor across about fifty thousand light-years of the galaxy. Because Terra is situated in the galactic west, the Astronomican does not cover the extreme eastern part of the galaxy. Warp travel beyond the Astronomican’s reach is severely limited – this creates the effective borders of the Imperium. Because of this, destroying the Astronomican would most likely halt all Imperial Warp travel within the galaxy, effectively bringing the Imperium to its knees.

Navigators, as well as other psykers, can sense the Astronomican. It is described as a sensation of silvery light and a chorus of many heavenly voices, beginning first with a solitary voice and progressively growing into an angelic choir. It is suggested that “pious marines” who can hear the Astronomican can fall into a meditative trance when they focus on it. Space Marine Captain Gabriel Angelos occasionally entered a sort of battle trance when he heard the Astronomican while fighting, improving his prowess in combat for the duration.


The Astronomican, unbeknownst to the Imperium, is what is drawing the Tyranid Hive Fleets to threaten the Galaxy and all of the Imperium.

Right after the 13th Black Crusade and the appearing of a Great Rift, the Astronomican went out causing unrest and horror throughout the Imperium. This period, later called the Days of Blinding, varied wildly. On some worlds, there were mere days of blindness, in others there were months. It is presumed that some of the Imperial planets are still depraved of the Emperor’s Light. On Terra, the blindness lasted thirty-three days.

Adeptus Astronomica

The Adeptus Astronomica are members of the Imperial priesthood who maintain the psychic beacon known as the Astronomican, used by Navigators. The Astronomica works closely with the Adeptus Astra Telepathica and recruits from their ranks.

The Adeptus Astronomica is largely composed of psykers; its non-psykers are hereditary servants. The process of constantly transmitting mental energy ultimately destroys these psykers, though there are always more to take their place. This act, however, allows Imperial ships to travel through the perils of the warp at great speeds. The organization is based in Terra’s Forbidden Fortress, where even Judges and Inquisitors must receive an invitation to enter. The task of the Adeptus Astronomica is to train the young psykers they receive from the Adeptus Astra Telepathica so that they can serve in the Chamber of the Astronomican. The whole organization is a training institute run by a class of older members known as Instructors. Some of the Instructors are given the title High Instructor and given control of a certain area of teaching. The day to day tasks such as maintenance is taken care of by a body of administrative functionaries.

Recruitment & Service

The overall head of the Adeptus Astronomica is the Master of the Astronomican, who represents the organization as a High Lord of Terra. In terms of composition, the organization has an administrative elite along with a large pool of young trainees who will one day become part of the corps of ten thousand that power the Astronomican. These trainees are taught to release their psychic potential by way of mental exercises, which is a process that takes a few months. Afterward, they are called into the psychic battery in the Hall of the Astronomicon and can be called at any time as old members either die or fail. In this state, the trainees rarely last more than two or three months with a hundred dying every day while within the spherical chamber. This process sees their very lifeforce being slowly drained away by a strange apparatus at the focal point of the great spherical hall.

Though these individuals sadly give their lives away, it is the ultimate sacrifice needed for Humanity’s continued survival. Due to their duties, members of the Adeptus Astronomica are rarely seen off Terra though its leaders who are responsible for the continued use of the Astronomican are allowed to travel freely. Similar to the Adeptus Mechanicus, this organization is a monastic order, and its members wear clothing similar to religious devotees, which are blue and hooded. Those fully trained members have their heads shaven and are ready to receive the neural implants, which will one day drain their lifeforce to power the Astronomican.


Young psykers are initiated into the Astronomica as Acolytes. They are taught not just how to use and control their psychic powers but are introduced to the Lore of the Astronomican. They learn the value of their lives, study philosophy, and are gradually brought to an inner understanding of the universe and the nature of the warp. Those who achieve this mystic state become the Chosen and are eventually called to serve in the Chamber of the Astronomican.

The status of Chosen is considered a great honor. To fall short of attaining this goal is not a failure; rather they go on to become Instructors or are absorbed as administrative functionaries in the Forbidden Fortress. Those who do make it to Chosen status are considered above the Instructors and even the Master of the Astronomican. Their heads are shaven, and they wear yellow robes and the scarlet badge of the Chosen. The rest of their lives are spent in prayer and contemplation until they are called to serve in the Chamber of the Astronomican.

Learn more of the Navigators who are guided by the Astronomican


~ Adepts, let us give thanks to the Emperor for his brightest light in the darkness.

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