Caesar's Comet: The Comet of 44 B.C. and Caesar's Funeral Games. John T. Ramsey and A. Lewis Licht, with Foreword by Brian G. Marsden (Scholars Press, Atlanta, 1997). pp. 236. $27.95 (hardcover), $17.95 (paperback).
This excellent book is the product of a unique collaboration between an ancient historian (Ramsey) and a physicist (Licht), who have joined forces to analyse what can be known or reasonably conjectured about the great daylight comet that seems to have appeared in July 44 B.C. during the funeral games for Julius Caesar. Ramsey and Licht (R&L hereafter) have taken a large step forward in understanding the possible nature of Caesar's comet (the ancient name for which was "sidus Iulium'" or "Julian Star," named for the Julian family to which Caesar belonged), and the role that this comet played in the events that shaped the earliest political career of Caesar's adopted son and successor, Octavian, who later become the first Roman emperor, Augustus. It was young Octavian who paid for and presented Caesar's funeral games, and who seized the opportunity of promoting the comet as a divine portent of Caesar's apotheosis as the god Divus Iulius, thereby making himself the son of a god and fit to be the rightful ruler of Rome.
R&L's book is, therefore, very much historical; the astronomy in it, while novel and ground-breaking, serves the overarching historical emphasis. Part I examines the historical name of Caesar's funeral games. R&L argue that what Octavian presented in July 44 B.C. was not only funeral games (ludi funebres), but also a celebration of the festival that Caesar himself had instituted in September 46 B.C. under the name "ludi Veneris Genetricis" ("Game of Venus the Ancestress"). They argue that Octavian changed the date of this festival in 44 B.C. to July and combined it with funeral games. This is an original argument; hitherto, ancient historians have generally supposed that Caesar himself changed the date in 45 B.C. Furthermore, these games may also have been more loosely dedicated to celebrating Caesar's personal goddess, Victory. In later times the games were actually renamed the "ludi Victoriae Caesaris" ("Games of Caesar's Victory"), and continued to be celebrated in July, the month named for Julius Caesar. It appears then that Octavian's games of July 44 B.C. should be regarded as an extravaganza in celebration of the greatest glories of the Julian house: Caesar, Caesar's Victory, and Venus who was the mythic ancestor of the Julians. This, R&L argue, was the charged historical context in which the comet appeared, an event most opportune for Octavian.
Part II then examines the astronomy of Caesar's comet and the host of associated problems. The ancient observations come from two sources and from two different time periods. The Chinese recorded a comet with an 8° to 10° tail, visible in the evening sky near the Sun during late May and early June. We can plausibly locate this comet in the area of the sky between Gemini and Auriga. European texts next record a brilliant star-like object or comet, visible in full daylight and rising in the north at the 11th hour of the day (late afternoon). Between these two sightings, European records may also indicate the appearance of a "torch" (meaning either a type of comet or a meteor) moving from east to west.
Astronomers had traditionally assumed that Caesar's funeral games occurred in September. But that would make it impossible for the Chinese and Romans to have been viewing the same object: too much time would have elapsed between sightings. Classicists, on the other hand, have understood that Caesar's games occurred in late July. By pooling the knowledge of their separate disciplines, R&L have therefore been able for the first time to link the separate sightings.
By examining a simulation of the sky at Rome in the late afternoon of July 44 B.C., R&L have concluded that the comet probably appeared in the constellation Cassiopeia. And armed with two positions (Gemini-Auriga at the end of May; Cassiopeia at the end of July) as well as an assumption about the approximate perihelion date and distance, they can speculate about a possible orbit for Caesar's comet. It is reassuring that Brian Marsden has examined these methods and seems to find them acceptable (p. xiii of his judicious Foreword to their book; he also helped in their orbital research, pp. 125-6).
R&L also speculate about a possible light curve for Caesar's comet. They assume that the comet travelled in a retrograde orbit, reaching perihelion at about the time of the Chinese observation, and then sped away from the Sun and somewhat closer to Earth. Near perihelion it must have reached into the negative magnitudes to be seen close to the Sun after sunset. The most plausible light curve that R&L present (p. 123) has the comet reaching approximately magnitude -3 in May, when it appeared as an evening object, then fading to magnitude 5 by mid-July, during which interval it became a morning object and travelled across the sky from east to west, in accordance with the European observation of a "torch." After that R&L speculate that the comet experienced an outburst during the funeral games that raised its apparent magnitude to about -4. Such an outburst also accords with European texts, which hesitate whether to call the object a comet or a star, and describe it as looking like "a very large star that was surrounded with rays, like streamers on a garland" (pp. 162-5). This could perhaps be the description of material being ejected from the nucleus during the intense outburst.
All of this, it turns out, is physically plausible and comparable to the behaviour of modern comets, apart from one feature. It seems that no other known comet has ever reached such a high apparent magnitude during an outburst, although that may simply be due to the fact that no modern comet has experienced such a large outburst so close to the Earth (p. 72).
R&L's word does face one serious problem, which they frankly acknowledge: the number of coincidences that their scenario requires. Specifically, we are compelled to believe that at a major juncture of Western history a spectacular naked-eye comet just happened to appear and that it just happened to experience an unprecedented outburst. But more damaging is that the Chinese, while having observed this object several months earlier in a less interesting phase, completely failed to report it when it flared well into the negative magnitudes. And finally, the best and the most detailed contemporary source of Roman information, Marcus Tullius Cicero, whose surviving letters and speeches from the 40s B.C. number into many hundreds of pages, also completely failed to notice the comet despite the stir it seems to have caused at Rome.
The hypothesis of such a series of coincidences is "bound to arouse suspicion," as R&L admit (p. 95). They twice try to allay that suspicion (pp. 61-65; 95-117) by a series of ingenious arguments, and even consider the possibility that the July sighting was a propagandistic fabrication put forth by Augustus years later (pp. 61-65). Such a bald-faced lie was not Augustus' way; R&L rightly reject that possibility. Nevertheless, although their account of the comet and games makes good sense and deserves careful consideration and high praise, R&L's difficulty in finding a really satisfactory explanation for the absence of the Chinese and Ciceronian mention of the July comet suggests that more work on that problem may be possible.
The final portion of the book turns to the astrological implications of Caesar's comet. Here again R&L have made a significant and original contribution by recognizing for the first time that Caesar's comet would have risen as seen from Rome with Capricorn in the ascendant. This explains the previously cryptic remark review that it [the comet] had come into being for him and that he was coming into being in it" (p. 159). Capricorn was the astrological sign that Augustus considered most significant for himself. Thus, as R&L explain (pp. 147-53), the young Octavian seems privately to have interpreted the sidus Iulium as a portent meant for him, heralding his birth into the Julian family and his destiny as a great leader at Rome.
A series of useful appendices concludes the book. The most important of these (Appendix I) quotes all 33 of the Greek and Roman sources relating to Caesar's comet and games. These sources are presented in both the original languages and in English translation. The Chinese sources are also quoted (in English) on pp. 75-76 and p. 80.
Roger Ceragioli
University of Houston
Journal for the history of astronomy vol. 28, pt. 4, p. 348 (1997)