Archaeoastronomy, Ireland

Astronomy in Ancient and Medieval Ireland

Welcome! In this section of the Archaeoastronomy portal on Historia Vivens Web Adriano Gaspani presents the results of his years-long studies and on field researches devoted to Ireland. The series of articles and contributions here below tell us about the evolution of the astronomical knowledge and symbolism in Ireland from the prehistoric times to the Celtic and then Medieval and Christian Age. A great opportunity to experience together a fascinating journey through the culture, traditions and nature of the wonderful “Emerald Isle”.

Image: Adriano Gaspani pictured while carrying out archaeoastronomical surveys on Inis Mor (Aran Islands).

Thanks to its natural isolation, for a long time Ireland has not been influenced by the typical features and ideas of the Greek, Middle Eastern (Arab), Egyptian and Roman astronomy, that was introduced only in later times through the work of the Irish monasticism. The Irish monks, the so-called "white martyrs", who sacrificed their lives leaving their own country for long missionary journeys travelling to far-away lands across Europe and the Mediterranean area where to share the gospel. When these monks happened to come back to their monasteries in Ireland, they brought with them the knowledge and the many manuscripts they acquired while traveling...

Here below you can find Adriano Gaspani's contributions (mostly in Italian language) published on Historia Vivens Web. Texts and images, unless otherwise attributed, are provided by the Author himself, and are his copyright. Please note that, to ease the reading, all articles, in full version and usually accompanied by pictures and notes, are available for free and safe download in PDF format. We hope you will enjoy the contents and wish you a pleasant surfing experience. This section is constantly evolving, please come back often for the latest updates. Thank you!


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The Astronomy of Ancient and Medieval Ireland

The existence of an empiric astronomical knowledge and a certain degree of technology in prehistoric and proto-historical Ireland is nowadays widely accepted by the scholars. In this article Adriano Gaspani illustrates us the main features of the astronomical heritage that was once spread among the proto-historic people of Ireland. The original idea and depiction of the naked-eye visible universe, which developed in Ireland in the night of time, was passed down, almost unchanged, in the cultural traditions of the Iron Age and Middle Ages, and got eventually enriched and widened only later on, when the Classical and Arab astronomy were finally introduced in Ireland by the hands of the Irish monks...

Image: the complex of Newgrange in Ireland (public domain, source: Pixnio free images).

"L’Astronomia nell’Irlanda Antica e Medievale" by Adriano Gaspani

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Astronomy in Prehistoric and Protohistoric Ireland

During the Neolithic and the Copper Age, Ireland was inhabited by cultures who built large mounds, the so-called passage tombs, that were part of the great megalithic necropolis, such as Newgrange, Knowth, Dowth, Saggart Hill, Montpelier, Loch Craobh, and Carrowkeel among the others, as well as several spectacular circles of large stones, which are mainly spread in the southern area of the island. Those cultures were the custodian of a remarkable astronomical knowledge that they developed through the continuous and repeated naked-eye observation of the sky and its phenomena. Most of the Irish megalithic structures appear, in fact, to be astronomically oriented with great accuracy, revealing a significant interest by their ancient builders in determining the rising and setting points of the sun and the moon on the local natural horizon in the prehistoric times. The ancient cultures of Ireland developed over time a celestial sphere and certain rules of space distribution and time measurement, which were not only completely original, but represented also a quite advanced cultural heritage that was passed down orally until the time of the Christianization of Ireland, when it was definitely recorded by the Irish monks in their splendid manuscripts...

Image: stone circle in the Beara Peninsula, Ireland (copyright and source Dick Hewitson).

"an Nemgnacht": the astronomy of the ancient celtic Ireland

The Irish ancient astronomy, known as "an Nemgnacht", represents a system based on observation and calculation, which is perfectly functional like the Greek, Mesopotamian, or Hindu astronomy. The ancient people of Ireland developed their own, characteristic astronomy, combining an original concept of the universe, called "Domun", and a structure of the celestial sphere, called "Speur", while also inheriting the theoretical and empirical knowledge previously acquired by the Neolithic Age settlers, the same cultures who built the megalithic structures...
Image: the 8th century AD Tara Brooch, one of the most important works of early Christian Irish art, that was found in 1850 and is now kept at the National Museum of Ireland in Dublin (public domain, source: The Full Wiki).

"An Nemgnacht: La Sfera Celeste degli antichi Celti d’Irlanda"

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Astronomy in Bronze and Iron Age Celtic Ireland

During the Iron Age, Ireland was inhabited by tribes of Insular Celtic descent, who developed their own way of observing and interpreting the sky and the stars that were visible at naked eye, a system distinctly different from the one known and practised in Gaul and more generally in the continental Celtic world.

The druids of Ireland developed an indigenous celestial sphere, with different names for the Sun, the Moon, the stars, the constellations and the most striking astronomical phenomena. Although the profile of the constellations was the same one known throughout the Celtic world, different were the representations for each asterism. Furthermore, in the native celestial sphere of the Iron Age Ireland the constellations differed also from those typical of the Greek-Roman culture, which had not been absorbed by the Irish culture yet.

Image: "Druids of ancient England", from “Pictures of English History: From the Earliest Times to the Present Period” by Joseph Martin Kronheim (1810-1896), German-born lithographer and wood engraver. Public domain, source: Wikimedia Commons.

The Enigma of the Turoe Stone

The Turoe Stone, a cylindrical monolith of granite dating from between the first century BC and the first century A.D., is an example of insular Celtic art that transposes symbolically, according to a complicated cryptic style, the image of the sky observed by the Irish Celts in the first century BC.

Image: side-view of the Turoe Stone (copyright: Eileen Roche, source:


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Time measurement and calendar in Iron Age Ireland

The development of efficient time measurement systems necessarily leads to the practice of astronomical observations carried on for a long time and aimed to determine with sufficient accuracy the fundamental cycles shown by the stars and to learn their usage applied to the efficient management of religion, agriculture, navigation and political and social activities.

Until not long ago it was widely thought that the way to measure the time known in the Gallic world and more generally in the continental Celtic, as also archaeologically witnessed by the many fragments of the bronze tablet on which is engraved the Coligny Calendar, was applicable also to the time measurement practices spread among the Celtic people of Ireland before the advent of Christianity.

Image: a segment from the Coligny calendar (source: Laboratory of Antiquities Science section Computer Sciences for Ancient Languages - LILA - Scuola Normale Superiore, Pisa, Italy)

The Calendar used by the Celts of Ireland

This article provides an accurate reconstruction of the calendar in use in ancient Ireland (Eryu) and of the systems to measure, mark and make use of the time passing for agricultural, religious and social purposes.

Image: the "Stone Sundial" from the megalithic site of Knowth, Ireland (copyright: Ken Williams, source:


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The Sky on the Earth: holy sites and places of power in Ancient Ireland

During the Bronze Age Ireland was fragmented into a myriad of realms almost always at war with each other. The various tribes, formed by people characterized by a strong Celtic matrix, developed several concepts related to astronomy and the observation of the sky that were coded in the orientation and spatial distribution of the structures that made up the various royal sites, including in the "hillforts" of minor importance, as well as in the customs and traditions which were then preserved and passed down orally over the ages.

Picture: Lia Fáil, Stone of Destiny, the Hill of Tara, detail, copyright Bernd Biege.

In the Iron Age Ireland the sacred sites were built by the Druids on the basis of very strict rules in order to symbolically transpose the Heaven on the Earth. This way the powerful religious class of the druids posed itself as an intermediary between the people and the gods, and only interpreters of the gods’ will. For the Irish people, in fact, holy sites and places of power mostly coincided, in that the residence of a king was automatically also a sacred center, as the king, although not a deity himself, was anyway chosen according to certain divine signs that only the druids knew how to correctly interpret.

The ringforts of Ireland and their astronomical orientation

The ringforts, built between the fourth and ninth century AD, represent the oldest fortified structures and villages of Ireland, counting over 45,000 units throughout the territory. The analysis of the directions of the various ringforts shows a significant tendency to place their access openings towards the sunrise or the winter solstice on the local natural horizon, or according to the dates of the oldest traditional festivals of Samhain and Imbolc.

Image: aerial view of the ringfort Dùn Duchthabair (Black Fort).

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Tara, the ancient residence of the Kings of Ireland

The early news about Tara (Temair) come from some manuscripts dating VI century A.D. The site, located nearly the town of Navan, (Co. Meath), was the most important early Irish royal settlement. Archaeological excavation in recent years has shed considerable light on the character of this royal site and it have increasingly assumed a critical role in contributing to a greater understanding of the Irish Iron Age as a whole. Archaeoastronomical investigation, carried out during 2003 August, showed the existence of several lines directed toward the point of rising and setting of the Sun, the Moon and the brightest stars, at the local skyline.

Image: aerial view of the Hill of Tara in Ireland (source:


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Astronomy and astronomical symbolism in medieval Christian Ireland

The astronomical knowledge spread among the pagan Druids during the Iron Age and the related symbolism flew almost unchanged into the cultural heritage of the Medieval Christian Ireland. The Irish monks, real experts of calendars, conversion systems between a computus and another, as well as of time measurement methods, managed to render the ancient heritage in the peculiar orientation of their oratories and churches, but refined also their own significant astronomical knowledge by introducing original methods of sky observation. They modified and adapted the ancient concepts of space, time, and the sky, but also introduced new and equally original ideas, many of which are still present not only in the baggage of the traditions of the inhabitants of the "Emerald Isle", but also outside Ireland.

Image: detail of a painting of 1925 depicting the abbey ruins and the round tower on the island of Devenish, in the lake complex of Lough Erne, Northern Ireland (copyright and source: The Lordprice Collection via Wikimedia Commons).

Astronomy and early Christianity in Ireland

The main source of information concerning the Irish monastic astronomy comes to us from the analysis of the records and annals which were compiled in the many monasteries, and which do not only reflect the cultural heritage acquired, but also illustrate well the significant own contributions made by the medieval monks.

Image: the ruins of the Ardmore Cathedral in Ireland (copyright: John Armagh, source: Wikimedia Commons).


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The fear of the apocalypse: the astronomy of the Irish monks

The observation of the sky carried out by the Christian monks in the Irish monasteries during the Early Middle Ages was based on the comparison between what was observable in the sky then with the predictions from the Book of Revelation, as witnessed by the monastic annals themselves. While observing the sky the monks focused their attention on identifying sequences of astronomical phenomena that could be confirmed in the Book of Revelation in order to foresee the arrival of the end of the world.

Image: detail of the "Book of Kells" (source: Irish Times).


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The influence of the Arabic Astronomy in Ireland

In the twelfth century AD the Arabic astronomy, medicine and astrology came to Ireland thanks to the Christian monks and the laymen who had played the role of professors in the great European universities of Bologna, Padua and Montpellier. The first among the many texts rendered in the Irish language was Messahalla’s astronomical treatise, which was translated by an anonymous author around the year 1325.

Image: Astronomers at the Istanbul observatory assisting Taqi al-Din, brilliant sixteenth century scientist (Wikimedia Commons source - Ala ad-Din Mansur-Shirazi).


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The Reask monastic site

The charming Reask monastic site, located in the Dingle Peninsula, the archaeoastronomical analysis of which was carried out by the author during an on-field research in Ireland aimed at surveying the ancient monastic structures, provides us with the opportunity of an exciting time travel to discover the culture and astronomy of the early medieval Ireland.

Image: view of the Reask monastic site (copyright Nigel Cox - Geograph UK, source Wikimedia Commons).


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The Cloigtheach, the Irish round towers

The cloigtheach (literally meaning bellhouse), the typical circular stone towers, were built in Ireland and Scotland, at the time the Viking raids, near a church or a monastery and had the door facing the western door of the church itself. Their symbolic or defensive funct is still under investigation.

Image: the cloigtheach of the monastery on the island of Devenish, Northern Ireland (copyright James Yardley, source Wikimedia Commons).


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Traditions and feasts of the Irish year

The existence all the year round of many festivities, which boasts Celtic origin and are still celebrated today, is a fact known and well documented by the archaeological findings, the ancient history and the traditions still in use in many places in Ireland. Among the festivities celebrated during the Irish Celtic year four feasts in particular played a special significance concerning both the solemnity and the rituality.

These feasts were, in chronological order, Samhain, Imbolc, Beltaine and Lughnasa. The recurrence of Samain marked the beginning of the celtic new year and inaugurated the period during which it was the night to prevail on the day. Each of the other three feasts was aimed to celebrate a defined deity among the ones worshiped by the Celtic Iron Age people.

The celebration dates of the ancient Irish feasts were determined by the heliacal rising of certain brightest stars, i.e. Antares (Samain), Aldebaran (Beltaine), Regulus (Lughnasa), and finally the stars of the constellation of Pegasus (Imbolc), as it also happened for the Celts in Continental Europe.

Among the Celts, in fact, the seasonal division of the year was not based on the Sun, but on the stars. The heliacal rising of a star means the first day of visibility of that star in the light of dawn. The Christianization of Ireland, which took place in the Middle Ages by St. Patrick and the Irish monks, led the so-called "solarisation" of the feasts, which were artificially linked to some conventional fixed dates of the Julian calendar then in use: February 1 (Imbolc), May 1 (Beltaine), August 1 (Lughnasad) and November 1 (Samain).

The cycle of the year at Inis Mor - Arann isles

The communities of the islands Arann measure, since time immemorial, the weather in a particular year bistagionale division, typically Celtic, which has its roots nell'andamento climate, and is marked by "na feili Bliadna", the "party of 'year". The basic elements of such practices are the sea, the sky, the earth and stone.

Image: a view of the distinctive barren and rocky landscape of Inis Mòr.


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Credits & Navigation

Images: All images on this page are public domain or provided by the Author himself unless otherwise stated.





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