The Great Christ Comet
Page 61
27 Nick James and Gerald North, Observing Comets (London: Springer, 2003), 23.
28 Yau et al., “Past and Future Motion,” 314, maintain that Halley’s Comet was first discovered at magnitude +4, but Swift-Tuttle at +3.4, and propose that the difference was due to Halley’s Comet having a tail at the point of discovery (making it easier to spot). Donald K. Yeomans suggests that generally a tailless comet must attain to +3.4 to become visible to the naked eye (“Great Comets in History,” http://ssd.jpl.nasa.gov/?great_comets [posted April 2007]). Since the Christ Comet was spotted extraordinarily early, it undoubtedly lacked a visible tail at the point of discovery—therefore it seems appropriate to assume a first sighting at +3.4. In his calculations of the brightness of the Bethlehem Star comet (personal email correspondence on September 28, 2012), Gary W. Kronk assumed discovery at +4 apparent magnitude. A first sighting of the Christ Comet at +4 magnitude would mean that it was slightly less intrinsically bright than the values given in our tables below.
29 However, David W. Hughes, “Early Long-Period Comets: Their Discovery and Flux,” Monthly Notices of the Royal Astronomical Society 339 (2003): 1103–1110, suggests that comets were often observed only when they reached an apparent magnitude of +2 (remember that, in the scale of astronomical magnitudes, a lower value means greater brightness).
30 John C. Brandt and Robert D. Chapman, Rendezvous in Space: The Science of Comets (New York: W. H. Freeman, 1992), 221; idem, Introduction to Comets, 105; Fred Schaaf, Comet of the Century (New York: Springer, 1997), 348; Mobberley, Hunting and Imaging Comets, 17; David Seargent, Comets: Vagabonds of Space (Garden City, NY: Doubleday, 1982), 39.
31 According to the analysis of Schmude, Comets and How to Observe Them, 32, and 35 table 1.7, the average value of n is approximately 4 for long-period comets, but closer to 6 for short-period comets.
32 Ibid., 35 fig. 1.40. Cf. Brandt and Chapman, Rendezvous in Space, 221.
33 Joseph N. Marcus, “Forward-Scattering Enhancement of Comet Brightness. II. The Light Curve of C/2006 P1 (McNaught),” International Comet Quarterly 29 (2007): 119, 124.
34 Schaaf, Comet of the Century, 349.
35 My translation of the Greek text in Emile de Strycker, La forme la plus ancienne du Protevangile de Jacques (Brussels: Société des Bollandistes, 1961), 168–170.
36 Passages in the Sibylline Oracles from the second or third centuries AD (which we have already cited) claim that the Star of Bethlehem was so bright that it was seen during the daytime. Sib. Or. 12:30–33 speaks of it as a celestial entity so extraordinarily bright that it shone forth in midday: “Whenever a bright star most like the Sun shines forth from heaven in midday, then indeed the secret word of the Most High will come wearing flesh like mortals” (J. J. Collins, “Sibylline Oracles,” in Charlesworth, Old Testament Pseudepigrapha, 1:445). Sib. Or. 1:323c–324 describes the Star as brightly shining in the broad daylight (J. L. Lightfoot, The Sibylline Oracles [Oxford: Oxford University Press, 2007], 311):
Then from the east a star in fullest day
(323c)
That brightly shines shall from the heavens beam
(323d)
Announcing a great sign for mortal men.
(323e)
Then God’s great son will come to humankind
(324)
In addition, Maximus the Confessor (early seventh century) maintained that Matthew’s Star could be seen during the daytime (Philokalia 2:92; see The Philokalia: The Complete Text, vol. 2, trans. and ed. G. E. H. Palmer, P. Sherrard, and K. Ware [London: Faber & Faber, 1981], 166–167).
37 It should be noted that larger celestial objects are easier for the eye to detect (Roger Nelson Clark, Visual Astronomy of the Deep Sky [Cambridge: Cambridge University Press, 1990], 12 fig. 2.5).
38 In our estimations of apparent magnitude here we have not taken allowance of the brightness boost due to the forward-scattering effect. As we shall see in the following chapter, the comet would have been something like 3.5 magnitudes brighter due to this effect at this point in time. When this is taken into account, the comet’s surface brightness, assuming n=4, would have been more like that of Saturn.
39 This was kindly highlighted to me by Andreas Kammerer, personal email message to the author, November 26, 2012. Andreas is a programmer of the Project Pluto Guide 9.0 software and a highly respected German amateur cometary astronomer.
40 Seargent (Sungrazing Comets) makes the point that, historically, the largest group of daylight comets consists of intrinsically bright comets with perihelion distances of 0.1–1.0 AU that have favorable forward-scattering geometry, such as Comet Skjellerup-Maristany in 1927.
41 The Biblical data may put a couple of constraints on the coma’s brightness: (1) Observers could tell that the meteor storm (Rev. 12:3–4), which we have dated to shortly before dawn on October 19, 6 BC, the eve of the celestial birth, was radiating from the tail of Virgo’s southern neighbor, the serpentine Hydra. Depending on the precise location of the radiant within the tail of Hydra and on the time of the meteor storm, some or all of the coma may have been above the horizon. If any of the coma was visible at the time, it was clearly not so intensely bright that it prevented observers from seeing thousands of meteors streaking across that third of the sky. However, even if the coma was present, its large size would have greatly diluted its surface brightness, with the result that it would not have bleached out the meteors. (2) On the day that the Magi made their way from Jerusalem to Bethlehem (between November 23 and 30, 6 BC), the comet was no longer visible during the daytime (“behold” in Matt. 2:9 implies that it had not been present during the day in advance of the Magi’s meeting with Herod). This absence could be explained by atmospheric conditions. However, it is also explicable with reference to the comet’s surface brightness being inadequate to render it visible during the daytime. Our analysis of the comet’s brightness and size at this point confirms that this was indeed the case.
42 Gary W. Kronk, “C/1882 R1 (Great September Comet),” http://cometography.com/lcomets/1882r1.html (last modified October 3, 2006).
43 At the time of writing, the sole exception is the comet discovered in 2002 by Kaoru Ikeya of Japan and Daqing Zhang of China, 153P/Ikeya-Zhang, which had been seen 341 years previously.
44 January 1–15 is “A,” January 16–31 is “B,” February 1–15 is “C,” February 16–29 is “D,” etc., with December 16–31 being “Y.”
Chapter 10: “Following Yonder Star”
1 As noted in chapter 9, we shall accommodate, in the tables, apparent magnitude values based on first observation of the comet at magnitude +3.4 within the period November 21–28, 8 BC, to December 10–17, 7 BC, and according to a brightness slope (n) of 3, 4, and 5. I have used Guide 9.0 to calculate the estimated absolute and apparent magnitude values. Unfortunately, Starry Night® Pro 6.4.3 assumes that n=3, which is lower than the average for both short-period and long-period comets.
2 Tail lengths in this chapter are derived using Project Pluto’s Guide 9.0. The tail length formula used by Guide 9.0 (and Starry Night® Pro 6.4.3) is based on “the average comet.” Andreas Kammerer, who developed the formula for Project Pluto, reckons that the software is accurate to within 30% in 80% of cases (http://www.projectpluto.com/update7b.htm#comet_tail [accessed March 26, 2013]). We have increased Guide’s tail length estimations by approximately 12.5%, since Guide estimates that the Christ Comet’s length on October 20 was about 160 degrees, but Rev. 12:5 would appear to indicate that at that stage the comet was approximately 180 degrees long. With respect to coma size, we have also based our estimations on Guide 9.0, doubling the coma diameter values to get an approximate length (major axis) of the elliptical coma. This takes account of the fact that the Christ Comet was not a small comet but rather a large one similar to Hale-Bopp. Kammerer notes that the formula he developed to calculate coma diameter for Guide comes to within 30% of the correct coma size for many comets, but does n
ot work for large comets like Hale-Bopp, considerably underestimating their coma size (ibid.). In personal email correspondence (October 30, 2012), Kammerer estimates that the major axis (length) of Hale-Bopp was approximately double what Guide 9.0 estimates. Since the Christ Comet was large and productive, like Hale-Bopp, I have adopted this simple approach in estimations of the size of the Christ Comet’s coma at different points of the apparition. This would suggest that the coma was about 11 degrees long on October 20, which, fittingly, is roughly the size of a newborn infant relative to its mother.
3 Nick James and Gerald North, Observing Comets (London: Springer, 2003), 135. Allowance must be made for the possibility that a comet’s brightness slope may change during the course of its apparition.
4 In this chapter I have used this software for determining the movements of the comet across the sky and the magnitude of stars, planets, and the Moon.
5 However, the Virgo illustration used by Starry Night® Pro 6.4.3 does not match any ancient conceptualization of Virgo.
6 The Babylonians called η (Eta) Piscium “the Ribbon of the Fishes” (N. A. Roughton, J. M. Steele, and C. B. F. Walker, “A Late Babylonian Normal and Ziqpu Star Text,” Archives of the History of the Exact Sciences 58 [2004]: 566). They conceived of the constellation in the same way as the Greeks—namely, as two fish connected by a long v-shaped ribbon or fishing line. See Gavin White, Babylonian Star-Lore: An Illustrated Guide to the Star-Lore and Constellations of Ancient Babylonia, 2nd ed. (London: Solaria, 2007), 216–217.
7 Assuming our orbital elements in the aftermath of the comet’s encounter with Saturn, prior to being exposed to the planet’s gravitational pull, the comet’s eccentricity would have been 0.9997, and its perihelion distance 0.127 AU, inclination 179.15 degrees, argument of perihelion 34.5 degrees, and longitude of ascending node 225.5 degrees. The backtracking was done by David Asher of the Armagh Observatory (personal email messages to the author, April 16, 19, and August 6, 2013).
8 See David Seargent, The Greatest Comets in History: Broom Stars and Celestial Scimitars (Berlin: Springer, 2009), 21–22.
9 Fred Schaaf, Comet of the Century (New York: Springer, 1997), 284.
10 In the case of Sarabat’s Comet of 1729, Father Nicolas Sarabat discovered it on August 1, 1729, but was persuaded that it was a comet rather than a nebulous star (namely, a cluster of hazy stars or a star in a haze) only after a couple of weeks of close observation with the naked eye (see Gary W. Kronk, Cometography: A Catalog of Comets, 6 vols. (Cambridge: Cambridge University Press, 1999–), 1:394).
11 The Babylonians divided up the zodiacal band from Aries to Pisces into 30-degree increments, each of which was given the name of one of the zodiacal constellations. The signs therefore corresponded approximately to the zodiacal constellations. The Babylonians do not seem to have been aware of precession of the equinoxes (the slight wobble of Earth on its axis). See Francesca Rochberg, Babylonian Horoscopes (Philadelphia: American Philosophical Society, 1998), 128, 131–133.
12 The astronomical references in the 7/6 BC Babylonian almanac, although inexact and inconsistent, seem to assume a zodiacal starting point of about 356.5 to 357 degrees. On February 5, 7 BC, therefore, Jupiter was crossing the boundary from the sign of Aquarius into that of Pisces.
13 The comet would have been within 3 degrees of Jupiter from January 15 until almost the end of February in 7 BC. Jupiter was 4.97 AU from the Sun on February 5, with an apparent magnitude of -2.03. The comet would have been about 7.7 AU from the Sun on February 5, 7 BC.
14 All this time, Mars was around the location of Virgo’s genitalia.
15 If the comet appeared for the first time on May 29, 7 BC, at an apparent magnitude of +3.4, its absolute magnitude would have been -6.9 (n=3) or -9.0 (n=4), or -11.0 (if n=5).
16 In Greek tradition the water is equated with, among other stars, κ, λ, φ, χ, ψ, and ω Aquarii—see Ptolemy’s Almagest, trans G. J. Toomer (Princeton, NJ: Princeton University Press, 1998), 377–378.
17 John Nolland, The Gospel of Matthew, New International Greek Testament Commentary (Grand Rapids, MI: Eerdmans, 2005), 110–111. However, Nolland goes on to speak of “Matthew’s miraculous star” (111).
18 As we noted above, Herod’s preoccupation with the Star’s first appearance might reflect a concern that the Messianic baby could have been born at that time.
19 New comets are generally discovered when the Moon is absent from the sky. Accordingly, if the comet was spotted in connection with the third and final conjunction, it would have been closer to the middle of December than its beginning.
20 From December 31, 7 BC, to January 9, 6 BC, the Christ Comet, according to our orbit, was within 3 degrees of Mars, coming to about one-third of a degree from it on January 4.
21 The precise moments when the comet disappeared and reappeared would have depended on its magnitude values as well as the visibility conditions.
22 This was a heliacal rising. Because the comet was visible for so long and moving against the backdrop of the stars, it had at least two heliacal risings in the eastern sky. Babylonian astronomers would have made records of the comet on each of these occasions. However, only the heliacal rising around the time of perihelion was particularly striking and profoundly meaningful.
23 According to our orbit, the comet was within 3 degrees of Mercury in the constellation Pisces from March 12 to 15, 6 BC, coming to within 1¾ degrees of it on March 14.
24 On March 28–April 3, 6 BC, it came to within 3 degrees of Venus, climaxing at about ½ degree from it on March 31. If it had become visible again by this point, the comet would have made for a beautiful celestial partner for the morning star.
25 Much-later Mandean tradition connects John’s nativity with the appearance of “a star that came and stood over Jerusalem” (Mandaean Book of John, chapter 18). See James F. McGrath’s translation, http://rogueleaf.com/book-of-john/2011/06/04/18-portents-of-the-birth-of-john-the-baptist (posted June 4, 2011). In this connection, it is interesting to note that the prologue of John’s Gospel appears to imply that some people identified John as “the light” (see John 1:4–9). In verses 7–8 the author emphatically denies that John the Baptist himself was “the light” and three times declares that John came as a witness to “the light.” These verses come between verse 5’s reference to the light shining in the darkness and verse 9’s reference to “the true light, which gives light to everyone, . . . coming into the world.” It is conceivable that one of the factors behind the apparent notion that John the Baptist was “the light” was the coming of the Star to the attention of the public around the time of his birth. This may have caused some to conclude that John was the fulfillment of the oracles of Balaam in Num. 24:17 and of Isaiah in Isa. 9:2.
26 If we assume n=4. If n=5, it would have been at least as great as the second brightest star, Canopus (-0.7).
27 If we assume n=4.
28 On July 31 a 16-day, waning-gibbous Moon would have risen over the western horizon just 10 minutes after the last part of the comet (the head) had risen.
29 Babylonian conceptualizations of the Great One could envision a water-jar next to each of the constellation figure’s feet and/or over his belly (see White, Babylonian Star-Lore, 122 fig. 71, and 123 figs. 72 and 73).
30 For pictures of jets of dust erupting from the Sun side of the comet, see Carl Sagan and Ann Druyan, Comet (New York: Pocket Books, 1986), 174–182; and Jürgen Rahe, Bertram Donn, and Karl Wurm, Atlas of Cometary Forms: Structures Near the Nucleus (Washington, DC: NASA, 1969), passim.
31 Assuming n=4. This does not take into account the effect of backscattering.
32 On the Babylonian constellation “The Great One,” see White, Babylonian Star-Lore, 121–123.
33 Assuming n=4.
34 See Robert Brown, Researches into the Origin of the Primitive Constellations of the Greeks, Phoenicians, and Babylonians, 2 vols. (Oxford: Willi
ams & Norgate, 1899), 1:67–76.
35 According to our orbit, on August 17, at sunset, the nucleus was less than a degree from σ Sagitarii (the Archer’s left shoulder). August 19 brought the nucleus midway between δ Sagittarii (Kaus Meridianalis) and λ Sagittarii, on the bow. It was where the Greeks and Babylonians imagined the Archer’s arrow.
36 Assuming n=4.
37 In Babylonian thought, β and δ Scorpii were two of three stars associated with the Scorpion’s head (Roughton et al., “Star Text,” 569)—evidently the third star was π Scorpii. The Greeks imagined the Scorpion’s forehead in the same location.
38 Gary W. Kronk: “The comet would have been seen in daylight from about 9 a. m. through the rest of the day” (personal email message to the author, September 26, 2012).
39 The Babylonian almanacs, predictions of astronomical events in advance, stated when each new month would begin (see, for example, the translation of the 7/6 BC almanac in A. J. Sachs and C. B. F. Walker, “Kepler’s View of the Star of Bethlehem and the Babylonian Almanac for 7/6 B.C.,” Iraq 46 [1984]: 47–49).
40 The Judeans’ employment of an observational calendar meant that the determination of when a new month began partly depended on the sighting of the new crescent Moon. Months were generally either 29 or 30 days. If there was a new crescent Moon on the 30th day and it was observed, the 30th day became the first day of the new month. If there was no sighting of the new crescent Moon after sunset on that day, whether because the Moon was too close to the Sun to be detectable or because atmospheric conditions meant that it was unobservable, the new month began on the following day. With respect to Rev. 12:1, the Moon’s location under the feet of Virgo indicates that September 15 in 6 BC is in view. If the new crescent Moon was not spotted on the evening of September 14, the new month, Tishri, would have been destined to begin the following evening regardless of whether the Moon was actually observed.