The Great Christ Comet (48 page)

In view of the large Jewish population in Bab­ylon, the Magi could have become aware of the coincidence of the celestial phenomenon and the Jewish calendar date. This may even have played a role in prompting them to appreciate that the cometary apparition had a particularly Jewish significance.

Perihelion

Since the comet was now coming close to the Sun and hence was more exposed to the solar wind and radiation pressure, its coma shrank in size.
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The visual effect of this in the sky was exaggerated because the comet was getting farther away from Earth. At the same time, the comet's brightness was building—not only was the apparent magnitude becoming progressively more impressive, but the smaller surface area of the coma was intensifying the brightness. In addition, as the comet began its slingshot around the Sun, the tail shortened as more and more of it moved behind the Sun, from Earth's perspective. This also intensified the brightness of the tail. All of this meant that the comet would have been an increasingly magnificent “evening star” in the days following September 15, although the fact that it was getting closer and closer to the Sun meant that it became increasingly difficult for humans to see the coma.

On September 23, as the comet was 0.2 AU from the Sun and beginning its hairpin turn around the solar disk, it found itself between Mercury and Venus. Venus, the comet, Mercury, and Earth were essentially in a straight line in that order. At that time the comet's 50+-degree tail would have been a striking feature in the evening sky, its last part only setting about 3 hours after sunset.

Between September 25 and 27, the nucleus was extremely close to the Sun from the perspective of Earth—within 4 degrees. Moreover, because the comet was essentially behind the Sun, the apparent length of the tail would have been relatively short. On the 25th, the end of it would have appeared for a brief time after sunset. However, no part of the comet would have been visible on the 26th.

According to our orbit, it was on the 26th, just before sunset in Bab­ylon, that, from Earth's perspective, the comet shifted from the west side of the Sun to its east side. Because of this, when it reappeared, it would be a feature of the eastern morning sky. It was around this time that the comet crossed its ascending node, that is, passed from south of the ecliptic plane, on which Earth orbits the Sun, to north of it.
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The comet had its perihelion on September 27.
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As with all comets, its speed on its orbit was greatest at perihelion, when it was midway through its astonishing U-turn around the Sun (
fig. 10.21
). Because the comet was coming so close to the Sun, just 0.119 AU away from it, the comet's activity may have increased dramatically from this point on.

The end of the comet's approximately 14-degree-long, intensely bright tail briefly reemerged over the eastern horizon shortly before sunrise on that day. The comet as a whole (not the coma) had started to rise heliacally; the scepter was beginning to emerge over the eastern horizon. The nucleus was at this point just 2 degrees from the Sun and so the coma and the sunward side of the tail were probably not detectable.

The comet was about 40 degrees long in the run-up to dawn on September 28. The comet's apparent magnitude was at least -15.5! (Remember that the full Moon's magnitude is -12.6.) The end of the very bright tail, which stretched back as far as Mars in the hind part of Leo, would have begun rising 3½ hours before dawn. It would have been a striking sight. Part of the gloriously brilliant coma might theoretically have been glimpsed in advance of the rising Sun, although the comet nucleus was still very close to the Sun—about 5½ degrees from it.

Based on Revelation 12 and Matthew 2, however, we suggest that the coma was probably not spotted in Bab­ylon or Judea at this point. This, of course, may be readily explained by the coma's proximity to the Sun and/or disadvantageous atmospheric conditions, whether because of cloud cover
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or sand and dust in the atmosphere.
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Nevertheless, such was the intense brightness of the area around the nucleus that those under clear skies who shielded their eyes from the Sun might have been able to see it at some stage through the day.

Virgo's Baby

What occurred from September 29/30 to October 22 in 6 BC was surely one of the most amazing astronomical phenomena in history: each morning, in the time leading up to sunrise, as Virgo's womb rose over the eastern horizon, the cometary coma played the part of Virgo's baby in a magnificent celestial birth scene to mark the nativity of the Messiah.

The Baby in Virgo's Womb

In the immediate run-up to dawn on September 29, when the nucleus was 0.15 AU from the Sun in outer space and just over 8 degrees from the Sun in the visible sky, and the comet had an apparent magnitude of at least -14.8 (see
table 10.2
),
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the coma, or at least part of it, could have been spotted by observers in
clear skies. The coma was very low in Virgo's womb and edging higher. The comet, with its long tail sticking up near-vertically, would have been about 65 degrees in length, making for a truly grand spectacle. It looked like a magnificent scepter (see Num. 24:17: “a scepter shall rise”).

To those able to see it through the daytime, the condensed brightness of the part of the coma around the nucleus may well have been a stunning sight. Not only was the comet's apparent magnitude surpassing that of the full Moon, but its surface brightness would probably have been greater than that of the full Moon. The coma in length was possibly a little less than the Moon's diameter. Any glimpse that the Magi might have got of a very bright occupant in Virgo's womb during the day would certainly have grabbed their attention and whetted their appetite for what was to follow. But observers would have struggled to get a good look at it, because it was still so close to the Sun.

When the cometary coma rose over the eastern horizon on September 30, some observers like the Magi were evidently astonished that it looked like a glorious and perfect baby within the womb of Virgo (
fig. 10.22
).
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The comet had moved farther from the Sun, with the result that the coma was appearing in a darker sky—it was now 10 degrees in altitude at sunrise. The oval coma at its longest would have been about the Moon's diameter.

The baby would have seemed to be head-down. The cometary coma had transformed Virgo, making it look like she was well into a pregnancy. It would have been natural to reflect on recent celestial history for a narra
tive explanation of the conception; the recent clothing of Virgo by the Sun may have seemed to provide the obvious cause.
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