THE PASSAGE AND THE CONSTELLATION:

The cross shape of the constellation does not form two perfectly straight intersecting lines. The “east-west line” of the formation is crooked because the central star, Sadr (Gamma g Cygni) was off line.

The longer “north-south line” running from Deneb at the north to Albireo at the south also deviated, and was seen to bend towards Sadr and back again towards the star Eta (h)Cygni. This bending of the north-south line is actually quite appropriate when viewed in the context of the Newgrange passage, which veers slightly to the east and back again as it winds towards the entrance.

But the most corroborative evidence to link the two was the star Albireo, which, as outlined earlier, represented the beak of the swan. In the context of the Newgrange passage, Albireo lay in the passage towards the south. This, we remembered, was the direction from which the sun’s rays penetrated the passage and chamber on the morning of Winter Solstice. The correlation of the yellow colour of Albireo, the yellow rays of the sun, and the yellow beak of the Whooper Swan was immediately obvious. We now had a link, albeit a tentative one, between Cygnus, the constellation, and Newgrange.

NEWGRANGE AND FOURKNOCKS:

On the morning of Winter Solstice, about four and a half minutes after the sun rises over Roughgrange Hill, or Red Mountain, the sun shines into the roofbox over the entrance to Brugh na Bóinne (Newgrange) and into the passage, where it illuminates the chamber which is 18 metres inside the mound.

This precisely calculated event, which doubtlessly involved huge effort for the Neolithic community which constructed the mound and its passage which acted as a calendrical device, is now the most heralded cosmic event in the modern archaeological world, and is known about right across the globe.

A line of investigation connected with the azimuth of the Newgrange passage was to lead us to the key with which we unlocked the entire enigma. This key was the Newgrange-Fourknocks alignment and its subtle but strategic connection with Deneb, the bright star of the “Northern Cross”. We had heard that the smaller neolithic mound of Fourknocks, which lies 15km southeast of Newgrange, actually lies directly on the path of this winter solstice azimuth from Newgrange. In other words, if you take an Ordnance Survey map and draw a line from Newgrange to Fourknocks, it corresponds with an azimuth of approximately 136 degrees. And so it would seem that Fourknocks may have been positioned in such a way as to form a special alignment with Newgrange and the winter solstice sun.

What we wanted to resolve was whether the passage of Fourknocks was aligned on a significant star, or constellation, given that its azimuth put it too far north of the sun's midsummer rising position, and the major northerly standstill of the moon.

The "window" of visibility from the passage of Fourknocks sits over the western slopes of the hill of Mullaghteeling, and in the distance can be seen some of the peaks of the Mourne and Cooley Mountains. When we consulted our computer software to "reconstruct" the skies over Neolithic Ireland, we wanted to view this area of sky just as the mound builders would have seen it at around the time the great mound at Newgrange was constructed.

Using SkyGlobe, a computer program designed to allow the user to see the positions of the sun, moon, planets and stars at any moment in time, we honed in on the critical time when we felt we would see something important - not the later end of the Fourknocks construction window, but rather the earlier possible date for its construction – 3,000BC – not long after the probable completion of Newgrange. We centred on the year 3,000BC. Then we watched as SkyGlobe performed a sequential, simulated movement, of the stars.

As the sequence progressed we watched with anticipation as some relatively faint and obscure stars and constellations passed close to our sky "window". Among the close grazers were Serpens Caput, a comparatively faint constellation, a magnitude 3.3 star in Lyra called Sulafat, Epsilon Cassiopeiae with a brightness of 3.4, a magnitude 2.6 star called Zosma in Leo, and a magnitude 3 star in Virgo called Vindemiatrix. But one star, alone in its brightness and its exact positioning in the centre of our window, dominated the pattern.

It is difficult to express the range of emotions I felt and the thoughts that went through my head as I watched Deneb, the bright tail star of the swan constellation, Cygnus, skim the horizon due north and then rise up slowly again, passing right through our neolithic "sky window". The very constellation which we had associated through various lines of investigation with the Newgrange mound, was now a found to be a target of the Fourknocks construct. This bright star, the main star of Cygnus, must have been a beacon of light in the dark northern skies of the neolithic.