Astronomy | Sirius, the Dog Star, shone into Newgrange when it was built

Newgrange is famously aligned so that the rays of winter solstice sunrise enter its roof box and shine deep into the chamber. But was it also built so that the chamber could capture the light of the Dog Star (Sirius) in prehistory? And was this suggested in mythology? Anthony Murphy investigates.

In Island of the Setting Sun: In Search of Ireland's Ancient Astronomers, first published in 2006, Richard Moore and I suggested that in addition to the sun, there were other objects that could shine into Newgrange. These included the moon and Venus, and our research showed that both these planets would indeed line up so that they could be seen from the floor of the chamber of the monument at certain times. We also suggested that there was one other significant object that was transiting the Newgrane sky window at the time it was built – the star we know today as Sirius, the Dog Star, the brightest of all the stars.

A Sirius alignment

We demonstrated how Sirius shared the same rising place as the winter solstice sun back in the Neolithic. One question is whether a Sirius alignment was coincidental with a winter solstice alignment , or whether it might have been part of the overall plan of the astronomer builders – to allow the sun's rays in on the shortest days, but to also witness the transit of the brightest star across the aperture or roof box opening at night.

Newgrange was a good location from which to observe the rising of the Dog Star, because Red Mountain, the hill on the south side of the Boyne Valley, provided an elevated horizon which meant that when Sirius became visible above its crest, it was already at an altitude that took it out of the haze and atmospheric compression which can prevent even bright stars from being seen at the moment of their rising.

Star risings are notoriously difficult to observe when you have no elevated or false horizon between you and the actual horizon. This was negated by the careful positioning of Newgrange, facing the ridge of Red Mountain. By the time Sirius is visible, rising over the hill, it is out of the "obscure" zone and is already more than 15 minutes off the real horizon.

The people who erected Síd in Broga (Newgrange) would doubtless have considered Sirius a very important star. It is just on the edge of the Milky Way, which was known as Síog na Spéire (Streak of the Sky), Bealach na Bó Finne (the Way of the White Cow) or Earball na Lárach Báine (The Tail of the White Mare).

In 3150BC, the declination of The Dog Star was -23° 2' 43.1", enabling it to be visible from the Newgrange chamber. However, the effects of Precession of the Equinoxes, combined with the proper motion of Sirius, meant that just two centuries later, around 2950BC, the declination of -22° 19' would have taken Sirius out of the sky box because its elevation was too high.

Is this what the pale light of a bright star or the moon might look like in the passage of Newgrange?

Engravings on kerb stone 52, which is at the rear of Newgrange, could be interpreted as representations of Orion's belt and the Dog Star. On the right-hand side of the stone, there are three sets of three circular holes, or cup-marks. Each of these sets of holes is contained within a double oval-shaped cartouche. There are a number of other large cup-marks on the stone, most notably one contained within a vertial line or stripe which runs down the centre of the stone and appears to divide the megalithic art into two separate panels. Is this giant cup-hole Sirius, in alignment with the axis of the site, which runs through the entrance kerb stone (K1), alone the passage and out the other side of the kerb at K52?

A diagram showing the possible representations of the Dog Star and Orion's Belt on kerb stone 52 at Newgrange.

Astronomy in mythology

It always excites me when I see something in mythology that appears to describe an astronomical function for one of these remarkable ancient structures. One spectacular example of this, (about which I have written a chapter for a soon-to-be-published anthology about the Dagda (1)) is contained in the Dindshenchas, where we read about the chief deity's illicit union with the goddess Bóinn:

Thither came by chance the Dagda
into the house of famous Elcmaire:
he fell to importuning the woman:
he brought her to the birth in a single day.

It was then they made the sun stand still
to the end of nine months – strange the tale –
warming the noble ether
in the roof of the perfect firmament.

The "house of famous Elcmaire" is Newgrange. Dagda is very much a solar deity. They "made the sun stand still" (winter solstice) while Dagda (sun beam) enters the house of Elcmar (Newgrange) and impregnates Bóinn (Brú na Bóinne = the Womb of Bóinn). Absolutely fascinating. Here, in myth and symbolic language, we have a poetic description of the winter solstice illumination of Newgrange.

In the past 48 hours, I have found another reference in myth which appears to describe, in the same sort of symbolic language, a possible illumination of the chamber of Newgrange by the Dog Star. I recently purchased two volumes of the Irish Texts Society's translations (by R.A.S. Macalister) of the Lebor Gabála Érenn (The Book of Invasions). 

R.A.S. Macalister's translation of Lebor Gabála Érenn (commonly known as the Book of Invasions).

Buried in a poem which appears to have been the very last in the first redaction of Section VII, the Tuatha Dé Danann, are two lines which are exceptionally intriguing. The poem is about Tuirill Bicrenn (from the story the Tragedy of the Sons of Tuireann). The two lines that jumped out at me are as follows:

Ethliu came into the Brug
in disguise in the form of a lapdog.(2)

Who is this apparently mysterious Ethliu (also spelt Ethlenn in the Irish)? She is, according to James MacKillop (3), the wife of Elcmar. In other words, Ethliu or Eithne (there are several variants of her name) is another name for Boand or Bóinn. 

So Bóinn/Ethliu came into the Brug (Newgrange) in the form of a lapdog/dog. Only in the late Neolithic did the Dog Star shine into Newgrange. By the time the Bronze Age begins, Sirius is too high in the sky and it can no longer be seen from the chamber, by an observer who, when the alignment was working, would need to have been prostrate, on the floor, looking down along the passage through the roof box.

It is a curious coincidence to our investigation that three dog skeletons were found in the chamber of Newgrange during Professor Michael O'Kelly's excavations. Prof. O'Kelly had speculated that these dog bones were recent, and represented animals which had entered perhaps through the roofbox and were unable to escape. However, recent examination of some of the dog bone from Newgrange shows that it is 4,800 years old. And it might have been from a domesticated dog. The Irish word in the original text of the Lebor Gabála is oirce or oircce, meaning a lapdog or a pet dog.(4)

Dagda casts his light magically on the womb of Bóinn.


It's all very fascinating, and suggests possibilities. But at this distant remove, we must accept that they are only possibilities. One of the greatest difficulties is that, apart from by circumstantial evidence, we cannot but imply or suggest a rough date of origin or epoch from which a myth originates. The Lebor Gabála was only written down in the 15th century AD. Who knows from what age its stories emanate?

But we can certainly entertain possibilities. John Carey, an academic and expert on Irish mythology and cosmology, gives us a fascinating observation about the accounts of cosmological magic at Brú na Bóinne:

"I am aware of no Irish legends associating the control or construction of sacred sites with the manipulation of time other than those which concern the tumuli of the Boyne valley".(5)

The myth of the Dindshenchas appears to describe symbolically the penetration of the male sun god's light into the feminine (and overtly uterine) stone interior of Newgrange, which was at one time mythically titled the House of Elcmar. This occurred, the myth says, when the sun was standing still in the sky, i.e. at the time of the solstice.

At the time Newgrange was constructed, the star we know today as the Dog Star (Sirius) shared the same declination as winter solstice sun. Bóinn/Eithne entered Newgrange disguised as a dog. It might all be just coincidental. But too often myth contains a core element of truth, a remembrance, perhaps, of long-distant events.


(1) The Dagda anthology is to be called Harp, Club, and Cauldron: A Harvest of Knowledge.

(2) Macalister (1941), Lebor Gabála Érenn Part VII, p. 285.

(3) Oxford Dictionary of Celtic Mythology, 1998.


(5) Carey, John (1990), Time, Memory, and the Boyne Necropolis, Proceedings of the Harvard Celtic Colloquium, Vol. 10.

Read More:

Read more about the astronomy of Newgrange in my book Newgrange: Monument to Immortality. You can buy a signed copy on my secure online shop.

This page was last updated on Wednesday, 1st August 2018 @ 23:50:47