Happy Fourth of July, everyone. The Fourth is actually a pretty important date for the study of Chaco, but in a roundabout (and somewhat controversial) way. It all has to do with a very famous pictograph panel below Peñasco Blanco at the west end of the canyon. While the interpretation of this panel is a matter of considerable debate, one way it’s been seen is as a record of an astronomical event that is known to have occurred during the height of Chaco’s power and influence: the supernova of 1054, which formed the Crab Nebula.
We know from several Chinese reports that the “guest star” resulting from the supernova first appeared on July 4, 1054 and continued to be visible day and night for almost two years. There are a few Japanese records of the supernova as well, along with one report from the Arab world. No clear-cut and unambiguous accounts are known from Europe or elsewhere in the world, although a few rock art panels in the Southwest have been proposed as representing the event. The most famous of these is the one at Chaco, which is often referred to as the “Supernova Pictograph” (even by the park itself in a sign at the site). It consists of three symbols painted onto the rock face in red: a hand, a crescent, and a starburst-like shape. It’s the starburst that has been interpreted as representing the supernova itself, of course, and the crescent has been seen as representing the crescent moon. On the morning of July 5, the moon, which was a crescent at the time, would have appeared in roughly the same relationship to the supernova, as seen from the pictograph site, as the relationship between the two symbols on the panel. Furthermore, the handprint points in the direction one would have looked to see this at at the time. The combination of the three symbols together, plus the fact that this would have happened at a time of considerable activity in the canyon, has led some to suggest that this pictograph panel was created to commemorate this historic event. The specific location may have been an established sun-watching position, from which the new star was seen unexpectedly and recorded.
Sign at the "Supernova Pictograph"
It all sounds fairly plausible as it goes, but there are some problems with this theory. Probably the biggest problem is that the specific set of symbols on the panel is known from ethnographic evidence to have been used by the Zunis to mark generic sunwatching sites, with the crescent representing the moon, the starburst representing the sun, and the hand marking the location as sacred. Now, it’s certainly possible that these symbols came to be associated with this activity as a result of the observation of the supernova at this site, but as far as I know there’s no reference to the supernova in ethnographic descriptions of astronomical observation at Zuni or any of the other modern Pueblos, so this is a pretty tenuous claim.
Furthermore, while the 1054 supernova would certainly have been noticeable at Chaco, there was an earlier supernova in 1006 (also recorded by the Chinese, and possibly by the Hohokam in southern Arizona) that was much brighter, and it’s not clear why the Chacoans wouldn’t have recorded that one too. It took place before the Chaco system really got going on a regional scale, but there was plenty of activity in the canyon during the 900s, so people there would presumably have seen it. It’s possible that it was recorded too, at some other site that hasn’t been found or that has disappeared in the thousand years that have elapsed since the event (note that the existing Supernova Pictograph has only survived because it was under a protective overhang), but again, there’s not any evidence for this. The Chacoans are definitely known to have kept careful track of regular patterns in the skies, such as the solstices and the lunar standstills, so they surely would have seen unusual events such as supernovae, but it’s not clear how they would have reacted to them or how inclined they would have been to record them.
View Looking East from "Supernova Petroglyph"
So it’s not really clear how to interpret the Chaco pictograph. I think the balance of evidence at this point leans slightly against it being a representation of the supernova, but I could be talked out of that position if some additional evidence for the supernova theory can be found.
Others, however, have proposed even more extreme theories based on the 1054 supernova. Among the more noteworthy of these is a proposal by Timothy Pauketat and Thomas Emerson, in a 2008 article in the Cambridge Archaeological Journal, that the rather sudden florescence of the Cahokia site in Illinois around AD 1050 may have had something to do with the supernova. The theory they present is interesting, but hard to effectively support. For one thing, dating methods in the Midwest are much less precise than in the Southwest, so pinning down any event to the year is usually not possible. There is certainly a suggestive correspondence between the sudden rise of Cahokia and the supernova, however, and this is supported by the apparent use of stellar imagery and symbolism at Cahokia and the importance of the stars to later cultures in the area, so there may well be something to this.
Opening at Casa Rinconada That Channels Sunbeam at Sunrise on Summer Solstice
I’m a bit troubled, however, by the reliance of Pauketat and Emerson on evidence from Chaco and the way they interpret it. For one thing, they say that the Supernova Pictograph is “above” Peñasco Blanco, when it’s actually below it, and not visible from the great house itself. More importantly, they say of the effect of the supernova:
Some believe that this particular cosmic event, which left behind the Crab Nebula, was commemorated in architecture and iconography at the time or in subsequent years. The most compelling evidence for this comes not from the Cahokia region but from the American Southwest, where a tree-cutting date places the construction of the largest and most isolated ceremonial building in Chaco Canyon, Casa Rinconada (noted for its many astronomical alignments) to AD
Now, it’s true that there is a single tree-ring cutting date from Casa Rinconada that dates to 1054. This is, however, the only tree-ring date for the site, so while it’s plausible that it dates the construction of the site this definitely cannot be stated as definitively as Pauketat and Emerson state it here. There is no specific provenience information available for this beam, so there’s no way to tell how it was used and whether it can plausibly be said to date to the initial construction of the site. The general architecture of Casa Rinconada is consistent with a construction date in the 1050s, but without more specific information tying it to a specific year on the basis of one unprovenienced beam is unwarranted.
Looking through Solstice-Aligned Opening at Casa Rinconada toward Aligned Niche
Furthermore, even if Rinconada was built in 1054, that doesn’t establish that it was built because of the supernova. There was extensive construction in the canyon throughout the mid-1000s, associated with Chaco’s apparent rise to regional dominance, and this began well before 1054. The major expansion of Pueblo Bonito began by the 1040s at the latest, and various other construction projects at other sites in the canyon dates to this general period. Rinconada could easily have been part of this general process without any specific relationship to the supernova. Indeed, there’s nothing about Rinconada that seems to refer to the supernova, despite the various astronomical alignments (some of them controversial as well, it should be noted) identified there.
None of this means that the supernova didn’t have an important role at Cahokia, of course, and it doesn’t even rule out an important role at Chaco itself. It does mean, however, that developments at Chaco shouldn’t really be used as evidence for developments at Cahokia, even though the two sites are contemporaneous and Chaco can be dated much more precisely. Cahokia may well have risen as a result of the 1054 supernova, but neither the Supernova Petroglyph at Chaco nor the one tree-ring date at Casa Rinconada provides evidence that it did.
Pauketat, T., & Emerson, T. (2008). Star Performances and Cosmic Clutter Cambridge Archaeological Journal, 18 (1), 78-85 DOI: 10.1017/S0959774308000085
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