Today is the winter solstice. This is an important time here in Chaco Canyon. Judging from the practices of modern pueblos, where it’s no coincidence that many important dances and feasts take place around Christmas, New Year’s, and Epiphany, it’s likely that the solstice was a major event for their ancestors, the prehistoric Chacoans. And, indeed, there is evidence encoded into both the buildings that the Chacoans built and the petroglyphs that they pecked onto the rock faces in and around the canyon that the winter solstice was important to them. Although not all of the astronomical alignments proposed by the Solstice Project have been universally accepted even within the archaeoastronomical community, enough of them have checked out that the idea of at least some alignments is quite widespread and mainstream these days.
The most famous alignment is the “Sun Dagger” atop Fajada Butte, which is most commonly associated with the summer solstice but which also has (or, more accurately, had) a winter solstice alignment in which the main spiral is bracketed by two daggers of light, rather than being bisected by one dagger as on the summer solstice.
For all its fame, the Sun Dagger was actually not very precise. It didn’t mark the exact day of the solstice, just the general time of year including it. There are, however, many other alignments in the canyon that are much more precise. One of these involves one of the mysterious “corner doorways” at the most famous of the Chacoan sites, Pueblo Bonito.
While most of these doorways, which connect rooms diagonal to each other, have not been found to line up with anything, there is one that serves as a very precise marker of the winter solstice. At sunrise on the solstice, the rising sun casts a beam of light through the doorway. One edge of this beam lies exactly along the vertical line of the corner opposite the doorway. This alignment only occurs on the day of the solstice itself, although the beam begins to appear in the middle of October and gradually moves, day by day, until it reaches the corner on the solstice. It then moves back, day by day, until it disappears.
While the precision of this alignment is certainly suggestive, there are some questionable aspects of it. The most important is that the corner doorway connects two interior rooms. The alignment works today because the outer wall that would otherwise block sunlight from reaching the corner doorway has fallen down. If that wall were solid, as most of the walls of Pueblo Bonito are believed to have been, there would have been no way for the alignment to work at the time it was allegedly put into place. It’s possible, then, that this particular alignment just happens to be a wildly improbable coincidence.
There are ways to save the alignment, however, if one is so inclined (as many are). One option is to argue that the outer wall may not have gone up to the second story, where the corner doorway is. While this could technically be true, since the surviving parts of the outer wall are all from the first story, the surrounding rooms all have second-story outer walls surviving in part, and one of those would likely have blocked the path of the sunlight even if there were no second-story wall in the room right next to the corner doorway. The other, more plausible, argument is that there was a second corner doorway, aligned with the surviving one, in the outer wall. It’s true that corner doorways are exceedingly rare, and that none of the known examples is in an exterior wall. Furthermore, there are very few exterior doorways in Pueblo Bonito at all. Very little of the outer wall above the first floor has survived in most of the building, however, so it remains entirely possible, though unproven and unprovable, that there was a second doorway to facilitate the alignment.
If the corner doorway alignment at Pueblo Bonito is in fact genuine, one very interesting aspect of it is that the beam of light begins to come through a fixed number of days before the solstice and moves a little bit each day until it reaches its crucial alignment on the solstice itself. This would make it useful as a device for marking time until the solstice, which would have been a very important consideration if the solstice itself was the occasion of important events that required significant advance planning.
There are some other solstice markers, less problematic than the corner doorway, which seem to have exactly this function. From a vantage point at the northeast corner of Kin Kletso, a smaller, later site about half a mile to the west of Pueblo Bonito, the solar disk rises on the winter solstice right in a notch along the horizon.
There are alignments like this all over the canyon, tied to key features on the complicated horizon line that allow easy tracking of the sun’s movement through the year. What makes Kin Kletso notable, however, is that from a vantage point at the southeastern corner the sun rises in the same notch two weeks before the solstice, and if one were to move gradually northward along the wall every day for those two weeks the sun would continue to rise in that same notch. This would be a very effective way to count down the time until the solstice for planning purposes.
A notch seems just a little arbitrary, though. There are all sorts of horizon features, and the number of possible viewing locations is literally infinite. This is a common and partly unavoidable problem with archaeoastronomy in general: if you draw enough lines, something is going to line up. Luckily, in the case of Chaco there are some additional reasons to trust in the likely accuracy of at least some of the proposed alignments. Probably the most important of these is the fact that the modern pueblos have held onto a great deal of their traditional knowledge, and astronomical observation is a documented part of that. Some of the pueblos, notably Hopi and Zuni, have sunwatchers to this day, and while the details of their practices are generally considered sacred knowledge not to be divulged to outsiders, enough has become known in various ways to demonstrate a strong continuity with ancient evidence.
Another line of evidence has to do with the specific shapes of some of the horizon features. A notch isn’t always just a notch. One good example of this is at Wijiji, a site roughly contemporaneous with Kin Kletso but at the other end of the canyon.
From the northwest corner of Wijiji, looking across the plaza to the southeast, the sun rises on the winter solstice in a notch. The right side of this notch, from this perspective, happens to have the exact same inclination as the path of the sun, so as the sun rises, on this day and only this day, it appears to run along the side of the notch before continuing up into the sky to continue its journey. Definitive evidence for the reality of alignments? Certainly not. Suggestive of it? Certainly. An inspiring, thought-provoking phenomenon? No question at all.
While the extent and purpose of astronomical alignments will continue to be debated for quite some time, there’s no escaping the sense that the sky is an ever-present and awe-inspiring feature of Chaco Canyon. The sunsets are amazing.