by The Great Christ Comet- Revealing the True Star of Bethlehem (retail) (epub)
12. Duration of pregnancy. The cometary coma’s growth gave the impression that Virgo’s pregnancy was developing normally. Together with the fact that the baby, during the delivery, was observed to descend into the area of Virgo’s legs, and thereafter was seen completely below her womb (at the birth) and then at least once thereafter heading toward the Sun, this suggests that the coma remained wholly or partly within the confines of Virgo’s womb until about October 19.
13. The delivery. Dilation would have been regarded as coinciding with the cometary coma seeming to weigh down on Virgo’s pelvic floor (approximately the level on Virgo where 80 Virginis is), and delivery would have entailed the baby moving down over that level. This downward movement within Virgo was due to the comet’s movement relative to Earth—essentially the comet’s orbit straightened out after its sharp perihelion U-turn and hence it could no longer stay in sync with Earth.
14. Hydrid meteor storm. While Virgo was actively giving birth to the baby, but had not quite fully delivered it, observers in the Near East saw a predawn meteor storm (Rev. 12:3–4a). The storm was attributed to the action of Hydra’s tail, almost certainly because it radiated from there, probably from the upper section of the tail, between γ (Gamma) Hydrae and the part of the tail near where Corvus (i.e., the Raven, in Babylonian thought) perched. Evidently the meteor storm occurred when the upper section of Hydra’s tail was above the horizon and when the sky was dark enough for the dramatic meteor display to be visible to human observers. This meteor storm happened before Hydra “stood.” This standing refers to the point when π (Pi) Hydrae, the tip of the tail, was level with the horizon, so that all of Hydra was above the horizon.
15. The birth. The night after the meteor storm, for the first time since the baby had appeared in Virgo’s womb, no part of the coma rose in advance of Virgo’s vaginal opening. The whole baby could be seen below the level where 80 Virginis was but above the visible horizon. To those interpreting what they saw through the grid of messianic prophecy, it seemed that the Messiah was born at this very time.10 The birth was probably on or around October 20, 6 BC, which equates to Tishratu 6 in Babylon and Heshvan 5 or 6 in Judea (depending on whether the new crescent Moon was observed in Judea on the evening of October 14).11 Both Matthew and Revelation imply that the heavenly birth coincided with Jesus’s birth on the earth. It is most natural to conclude that the coma-baby appeared to be approximately the size of a newborn baby at the point of birth.
16. Iron scepter. At the point when the cometary baby was born, the comet’s tail was apparently extraordinarily long and possibly silvery-gray. The whole comet seems to have formed an “iron scepter” that stretched right across the sky to the western horizon.
17. Disappearance into the Sun’s light. In terms of the celestial narrative, the messianic child needed to be delivered from the grave danger posed by Hydra. This deliverance was communicated to Earth-dwelling observers when the cometary coma, after birth, quickly disappeared into the light of the Sun and below the horizon (i.e., it heliacally set).
18. From Babylon to Jerusalem. Having witnessed the entire celestial nativity drama, the Magi no doubt soon began their journey to Judea. The comet, having switched quickly from the morning to the evening/night sky, probably remained visible to them throughout their journey. It is likely that, every night, the comet moved toward and over the western horizon, seeming to urge them onward to Jerusalem.
19. South-southwest to Bethlehem. On the evening when the Magi traveled from Jerusalem to Bethlehem, approximately 30–40 days after the conclusion of the sign in the eastern morning sky, the Star reappeared, probably at sunset, in the southern sky. The Star seemed to go before the Magi to Bethlehem. Assuming a journey of 2 hours, the comet would have appeared in the sky to the SSE and moved to the SSW, the direction of Bethlehem from Jerusalem.
20. Dropping in altitude. After guiding them to Bethlehem, the comet, having passed its culmination (its highest point, on the meridian in the south), then dropped in altitude (“coming”; Matt. 2:9) until it seemed to “stand.”
21. Setting on the western horizon. The Star guided the Magi to one particular house in Bethlehem. We can deduce that the coma was close to the visible horizon at that stage and so was about to set.12 The house where Mary and Jesus were was evidently, from the Magi’s perspective, located along the skyline and was distinct from other structures. Since the Star “stood over” one particular house, it is most likely that at that time the comet had a near-vertical tail, 30–45 degrees long.
22. Subsequent behavior. There is no indication of the comet’s behavior thereafter. However, the fact that it was observable for so long prior to perihelion suggests that it could have remained visible for many months afterwards.
Determining the Orbit
We have already seen that astronomers have determined the orbits of many historical comets. In fact, we are in the fortunate position of knowing the orbits of comets as far back as the fourth and third centuries BC.13 Astronomers are able to calculate a comet’s orbit when they can derive sufficient positional information from the surviving records of observers. Remarkably, just three observations are adequate to determine the six orbital elements that fully describe any orbit. In the case of the Christ Comet, Revelation 12:1–5 provides more than enough observational data to make a reasonably precise determination of its orbital elements at that time. It is important to realize that only a comet with a very particular orbit can do what Revelation 12:1–5 describes. Everything has to be just right: the placement of Earth on its orbit around the Sun, the time and place of the comet’s perihelion, the comet’s inclination and the direction of its motion, and the whole orientation of its orbit. Accordingly, we are able to deduce the six orbital elements that describe the Christ Comet’s orbit (table 9.1; see fig. 9.1 for a portrayal of the comet’s orbit).14
Eccentricity
1.0
Perihelion Distance (AU)
0.119
Inclination
178.3
Argument of Perihelion
9.47
Longitude of Ascending Node
200.08
Perihelion Date
(Julian)
1719500.7/
September 27, 6 BC
TABLE 9.1 The orbital elements of the Christ Comet.
FIG. 9.1 The Christ Comet’s orbit viewed from the time of perihelion on September 27, 6 BC. The outermost circle is Uranus’s orbit. The green line is the comet’s eccentric orbit, and the orange arrows are directed to the First Point of Aries, a base line for astronomical measurements. The comet is under the ecliptic plane on its way toward the Sun and over it on its way away from the Sun. However, because the comet is so narrowly inclined, it is above the orbital paths of the major planets (other than Earth) on its way toward perihelion. On its way out, the comet is above the orbital paths of all the major planets except for Mercury (because of the significant tilt in Mercury’s orbit). Image credit: Sirscha Nicholl.
Of course, the big question is whether this orbit is compatible with what Matthew records concerning the comet’s behavior on the final stage of the Magi’s journey (Matt. 2:9–11). Astonishingly, it is. Shortly after the cometary baby’s birth in the eastern predawn sky, the comet shifts to the western evening sky and quickly migrates to the southern sky. 30 to 40 days after leaving the eastern sky, the comet is appearing at sunset in the south-southeast and, over the following couple of hours, is moving to the south-southwest, the direction of Bethlehem from Jerusalem. Then some 5 hours later it sets near-vertically over the western horizon. This remarkable compatibility is overwhelmingly strong evidence that our approximate orbit is correct, that Revelation 12:1–5 is indeed the key that unlocks the mystery of the Bethlehem Star, and that Matthew 2’s account of the Star is grounded in history.
Since cometary orbits are so susceptible to change due to gravitational and nongravitational effects, it cannot be assumed that a calculated orbit is app
licable a long time before or after the observations which were the basis of the orbit determination. In the case of the Bethlehem Star, our orbit suggests that the comet had a relatively close encounter with Saturn on the way toward the inner solar system and so the orbital elements before that would have been different.
Chronological Considerations
Before we consider the comet and its orbit in more detail, it is important to pause to fill in some of the chronological gaps in our knowledge based on our orbit. Our orbit suggests that the predawn celestial show in the east ended a couple of days after the birth, namely on October 22, and that this would have become evident to observers by October 23. We should therefore reckon on the Magi departing their homeland at some point between October 23 and 25. A quick departure is strongly supported by the observation that at that time the comet, having shifted to the western sky, becomes capable of functioning as a westward prompt or guide for the Magi.
In light of this and our earlier conclusions regarding the duration of the Magi’s journey (approximately 28–37 days) and their stay (2–5 full days, leaving on the 3rd–6th day), we are in a position to set out two scenarios regarding the chronology of the Magi’s visit to Bethlehem: either (A) it occurred in the week running up to the holy family’s trip to the temple (on November 29)—that is, the week of November 21–28;15 or (B) it took place in the week immediately following it—that is, sometime in the week following Mary and Joseph’s return from Jerusalem on the afternoon of November 29—that is, November 29–December 6.16 In Scenario A, assuming a departure date between October 23 and 25, the Magi’s camel caravan advanced approximately 17–18 miles per day toward Jerusalem and arrived in Bethlehem between November 23 and 25, and they departed on or before the 28th. In Scenario B, having left Babylon on October 24 or 25, the camel caravan got 15 miles closer to Jerusalem each day, and the Magi arrived in Bethlehem late on November 29 or on the 30th, in the immediate aftermath of Mary and Joseph’s return from Jerusalem, and departed for Babylon between December 2 and 6.
In our analysis we shall consider two representative dates for the arrival of the Magi in Bethlehem: November 23 (= an average journey speed of about 18 miles per day if they left Babylon on October 24); and November 30 (= an average journey speed of about 15 miles per day if they left Babylon on October 25), 6 BC.17
According to our reckoning, Herod’s decree to massacre the infants was issued on (or around) either November 30–December 2 or December 3–7, 6 BC. The Star’s initial appearance (1–2 Jewish luni-solar years before Herod issued his order) was therefore either between November 21–23, 8 BC, and December 10–12, 7 BC; or between November 24–28, 8 BC, and December 13–17, 7 BC.18
We propose, then, the following approximate chronology:
Between November 21–28, 8 BC, and December 10–17, 7 BC: The Star first appears.
September 15, 6 BC: The Moon is observed under Virgo’s feet.
September 29/30, 6 BC: The cometary coma rises heliacally in Virgo’s womb.
October 15, 6 BC: Virgo appears to begin active labor.
October 19, 6 BC: A meteor storm radiates from Hydra’s tail.
October 20, 6 BC: The cometary baby, having descended, has completely emerged from Virgo’s womb and so is regarded as having been born.
Between October 23 and 25, 6 BC: The Magi leave Babylon on their mission to worship the Messiah in Judea.
SCENARIO A
Between November 23 and 25, 6 BC: The Magi arrive in Jerusalem and, that same evening, are ushered by the Star to Bethlehem. Later that night the comet stands as it sets, pinpointing the house where Mary and Jesus are.
Between November 26 and 28, 6 BC: The Magi depart Bethlehem to return home to Babylon.
November 29, 6 BC: Mary, Joseph, and baby Jesus visit the Jerusalem temple on the 40th day to fulfill their religious obligations, and return to Bethlehem.
November 30–December 2, 6 BC: Herod the Great orders the Massacre of the Innocents in the vicinity of Bethlehem.
SCENARIO B
November 29, 6 BC: Mary, Joseph, and baby Jesus visit the Jerusalem temple on the 40th day to fulfill their religious obligations and return to Bethlehem.
November 29–30, 6 BC: The Magi arrive in Jerusalem and that same evening are ushered by the Star to Bethlehem. Then, later that night, the Star leads them to the house where Mary and Jesus are.
Between December 2 and 6, 6 BC: The Magi depart Bethlehem to return home to Babylon.
Between December 3 and 7, 6 BC: Herod the Great orders the Massacre of the Innocents in the vicinity of Bethlehem.
We must now turn to make some observations about the comet based on our orbital elements.
Long-Period Nearly Isotropic Comet
Within the category of long-period comets, the Christ Comet is a member of the broad family of “Long-period nearly isotropic” (NI) comets.19 Basically, this is all the long-period comets that are not part of the sungrazer class—sungrazers are reckoned to total about one-third of all comets (if one assumes that recent centuries are representative).20 The sungrazers have in common that they all approach within approximately 0.01 AU or 0.05 AU of the Sun. Astronomers also use a category of “sunskirters,” which includes all comets that have a perihelion distance that is less than 0.1 AU but greater than that of the sungrazers.21 According to our orbit, the Magi’s Comet came as close as 0.119 AU to the Sun, which is very close, but not quite as near as the sunskirters.
Narrowly Inclined NI Comet
NI comets have a wide variety of inclinations across the full spectrum of 0° to 180°. Strikingly, however, most NI comets whose orbits have been calculated have inclinations between 40° and 160°. Of those between 0° and 40° and between 160° and 180°, the smallest proportion fall within the 170–180° range.22 Therefore what we have in the Christ Comet may be relatively rare for comets—an essentially ecliptic, retrograde long-period comet. In this respect the Christ Comet, with its 178.3-degree inclination, is like Comet Lulin, the brightest comet in 2009,23 which had an inclination of 178.4 degrees. It is also reminiscent of Comet Tempel of 1864 (C/1864 N1), which had an inclination of 178.13 degrees and came to within 0.1 AU of Earth on August 8, 1864, moving from the eastern morning sky to the western evening sky at that time.24 Narrowly inclined comets sport relatively straight dust tails, from Earth’s perspective, as opposed to the more curved dust tails of steeply inclined comets. Of course, the tails of narrowly inclined comets are curved in outer space, but the curvature is not apparent to those on Earth because it occurs on the plane on which Earth orbits the Sun.
Reminiscent of Comet Hale-Bopp
The fact that the Christ Comet was seen by the naked eye so long before perihelion is reminiscent of C/1995 O1 (Hale-Bopp). Hale-Bopp was first seen 10½ months before perihelion, when it was still 4.37 AU from the Sun. It has been calculated that Hale-Bopp started forming its coma roughly 18 AU from the Sun.25 The Bethlehem Star comet was first observed on or before December 10–17, 7 BC, about 9½ months before perihelion, when it was 4.71–4.63 AU from the Sun. Its coma probably began to form out beyond the orbit of Uranus (20 AU from the Sun).
Comets such as Hale-Bopp and the Magi’s Star begin degassing so long before perihelion because they contain relatively high volumes of extremely volatile materials such as nitrogen, carbon monoxide, and methane.26 These materials begin reacting to the Sun at long distances from the Sun, whereas water-ice begins to degas only when within 3 AU.27
Brightness
Having determined an orbit, we must now turn to the matter of the Christ Comet’s brightness. A comet’s intrinsic brightness is called its absolute magnitude. Its brightness as it appears to observers from Earth at any given point in time is called its apparent magnitude.
The starting point of any investigation of a comet’s brightness is to determine the apparent magnitude at first observation. Investigations of ancient cometary apparitions have determined that a tailless comet must attain to an apparent magni
tude of about +3.4 to be observed with the naked eye.28 It seems wisest therefore to assume that the Bethlehem Star comet had a +3.4 apparent magnitude when it was discovered.29
Next, the pattern of development of the comet’s brightness must be estimated. Comets usually brighten exponentially as they approach the Sun. This increase in brightness is directly related to the increase in cometary degassing as the comet nears the Sun. The steepness of the rise in brightness as it nears the Sun and of the decline in brightness as it moves away from it is called the brightness slope, which is expressed as the value of n. The higher this value, the steeper the brightness slope is.
In the absence of adequate data to refine the pattern of cometary brightness development, scientists tend to assume that n=4.30 This assumption is based on the idea that this is the average value for comets.31 According to recent analysis by Schmude, long-period comets can have values of n from -2 to over 11, but most are grouped between 2 and 6, with the bulk of them concentrated between about 3 and 5, and the approximate average being 4.32 For example, while Bennett’s Comet of 1970 had a brightness slope of about 5, Hale-Bopp’s was about 3. Accordingly, anyone assuming that Hale-Bopp’s display in the inner solar system would abide by the average brightness slope n=4 would have been slightly (but not greatly!) disappointed.
In the tables accompanying my discussion of the Christ Comet’s apparition, I shall offer brightness estimates based on the following values of n: 3, 4, and 5. It is likely that the brightness slope of the long-period Bethlehem Star comet comes within this range of values.
In establishing the correct value of n, we have more to go on than merely estimates based on the comet’s probable apparent magnitude at first observation—we have data regarding the comet’s performance in the inner solar system. Just as the astronomical community modifies the value of n in response to further observations of the comet after discovery, so also we are in a position to narrow down the brightness slope of the Bethlehem Star comet based on what we know of its behavior around the time of its closest encounter with the Sun.