The Great Christ Comet (54 page)

As the comet set between November 23/24 and November 30/December 1, Jupiter was above the coma in the constellation Aries, 42½–45 degrees off the horizon, while Saturn, in the constellation Pisces, was even closer to the coma, hovering just 20½–22½ degrees above the horizon, approximately halfway between the coma and Jupiter. The comet's impressively long tail would have extended upwards from the horizon right past Saturn toward Jupiter. To someone surveying the scene as a whole from the Magi's perspective, around the time of the comet's setting, the tailed comet would have seemed like a massive pointer directed downwards from Jupiter, past Saturn, to the Messiah's house. It may have looked as if Jupiter was pinpointing the location of the Messiah, the one destined to reign on behalf of Israel, represented by Saturn. This was an awesome climax to the Magi's journey, and indeed to the entire cometary apparition.

Of course, the comet had first appeared during a year dominated by the three Jupiter-Saturn conjunctions of 7 BC (climaxing on May 27–31, September 26–October 5, and December 1–8). Indeed it is very possible that the Bethlehem Star was first observed in connection with one of those conjunctions. In light of this, the fact that Jupiter and Saturn were present for the climax of the comet's apparition may well have been deemed especially significant. The Magi may already have come to the settled conviction that Jupiter had played the part of the Most High God, Saturn the role of Israel, and the “star” that of the one destined to exercise sovereignty over the earth on behalf of Israel. Needless to say, if the comet did first appear during the Jupiter-Saturn triple conjunction, this climactic scene in Bethlehem would have meant that a beautiful celestial inclusio bracketed the whole cometary apparition.

The comet, the coma of which had played the role of the messianic baby in Virgo in the great celestial drama in the eastern sky just over a month before, had now led the Magi to the very building on the earth where the baby was.

11

“Brightest and Best of the Sons of the Morning”

The Greatest Comet in History

What the Bethlehem Star comet did in 7–6 BC was astonishing and obviously unique. It was clearly a magnificent comet, but how does it compare with the other great historical comets?

The Marks of Great Comets

In an earlier chapter we set out the marks of great comets. They must have some, if not all, of the following characteristics. They should (1) make a close pass by the Sun, no more than about 1 AU from it; (2) make a close pass by Earth; (3) provide good viewing opportunities for human observers; (4) be very productive; (5) have a clearly visible tail, at least 10 degrees in length; (6) have a large nucleus and notable coma; and (7) be at least as bright as the sky's more distinguished stars. Some great comets may have deficiencies (e.g., they may be farther from the Sun and/or Earth), but their other traits will make up for these.

The Christ Comet has all the marks of a truly great comet. Indeed its qualifications for greatness supersede those of any other comet in recorded history. It is quite simply the greatest of the great historical comets.

A Close Pass by the Sun

The Bethlehem Star Comet came as close as 0.119 AU, or 17.8 million km, from the Sun. In the league of the Great Comets, as established by Don Yeomans in April 2007,
1
it would be 8th out of the 66 in this regard.
2
It is superseded only by sungrazers—the Great Comet of 1680 (0.006 AU)
3
and established members of the Kreutz sungrazing family, specifically the Great March Comet of 1843 (0.0055 AU), the Great September Comet of 1882 (0.00775 AU), and Ikeya-Seki in 1965 (0.0078 AU)—and two sunskirters, the Great Southern Comet of 1865 (0.026 AU) and the Great Comet of 1668 (0.07 AU), and by one NI comet, the Great Comet of 1665 (0.106 AU). The 6 BC Comet's perihelion distance
is slightly closer to the Sun than Messier's Comet of 1769 (0.123 AU), which had a tail of over 90 degrees,
4
and the Great January Comet of 1910 (0.13 AU), which sported a 50-degree tail. It is worth remembering that the Great Comet of 1811 achieved greatness even though it was 1.04 AU from the Sun at perihelion, and the magnificent Hale-Bopp made it only to 0.91 AU from the Sun.

A Close Pass by Earth

As regards making a close pass by Earth (perigee distance), the Christ Comet came as close as 0.1045 AU, or 15.63 million km, on October 24/25, 6 BC. In that regard it would rank 12th in Yeomans's list of great comets. The great comets ahead of it in perigee distance are Halley's Comet in 837 (0.03 AU), followed by the Great Comet of 1132 (0.04 AU), the Great Comet of 1472 (0.07 AU), the Great Comet of 1556 (0.08 AU), the Great Comet of AD 400 (0.08 AU), Halley's Comet in AD 374 and 607 (0.09 AU), the Comet of AD 568 (0.09 AU), Hyakutake in 1996 (0.1018 AU), the Comet of AD 390 (0.1037 AU), and Halley's Comet in 1066 (0.104 AU).
5
It should be noted that 4 of these 11 are different apparitions of the same comet, 1P/Halley. When one considers how magnificent the great comets of 1807 and 1811 were, when they came no closer than 1.15 AU and 1.22 AU respectively from Earth, and how stunning Hale-Bopp was, even though it never came closer to Earth than 1.32 AU, one begins to appreciate the significance of the Christ Comet's high perigee ranking. Moreover, it should be remembered that the Christ Comet actually made two close passes by Earth—on August 14, 6 BC, on its way toward perihelion, it came as close as 0.334 AU to Earth.

A Combination of Close Passes by the Sun and by Earth

When one considers the perihelion and perigee distances together, the Christ Comet emerges at the top of the list.

Of the 7 great comets with perihelion distances closer than that of the Christ Comet, the one that came nearest to Earth was the Great Comet of 1680 (Kirch's Comet)—it was 0.42 AU away. The next closest was the Great Comet of 1665, which came to about 0.57 AU from Earth.

Of those great comets that came as close to Earth as the Christ Comet, or closer, the ones that came nearest the Sun were the Great Comet of AD 400, which was only 0.21 AU from the Sun, Hyakutake (
fig. 11.1
), whose perihelion distance was 0.23 AU, and the comets of 1471 and 1556, both of which came as close as 0.49 AU to the Sun.

When one considers the perihelion and perigee distances of all of Yeomans's great comets, it is the AD 400 comet that holds the record—0.21 AU from the Sun and 0.08 AU from Earth. After it comes Hyakutake—0.23 AU from the Sun and 0.1 AU from Earth—and then Great Comet of 905—0.2 AU from the Sun and 0.21 AU from Earth.

In its combination of perihelion and perigee distances—0.119 AU and 0.1045 AU respectively—the Christ Comet surpasses even the Great Comet of AD 400. It is worth discovering a little more about that comet.

Like the Christ Comet, the Comet of AD 400 made its closest approach to Earth after perihelion. Philostorgius
6
referred to this comet as a “star which appeared in the form of a sword,” and Socrates Scholasticus
7
mentioned that it was a huge comet of extraordinary magnitude that stretched from the sky to the ground, something unprecedented for those alive at the time.
8
Hermias Sozomen
9
described it as having “extraordinary magnitude” and being “larger . . . than any that had previously been seen.”
10
David Seargent points out that it “holds the record for a double bill of small perihelion and small perigee.”
11
He also suggests that its coma was “several degrees in diameter,” that its tail stretched “like a broadening beam of light across tens of degrees of sky,”
12
and that it would have cast such strong shadows that people would have been able to read by its light.
13
Gary Kronk estimates that this comet had an absolute magnitude of only +6,
14
with a maximum apparent magnitude of around 0. However, the fact that this comet was described as simultaneously massive and of extraordinary brightness suggests that its apparent magnitude peak must have been much greater than this. It is possible that the comet had a temporary but dramatic flare-up in the aftermath of its closest approach to the Sun, and that this fizzled out within a couple of weeks of the comet passing Earth. At the same time, Seargent points out that an unimpressive absolute magnitude might have been partly compensated for by the fact that the comet's angle with respect to the ecliptic was becoming ever narrower throughout the apparition.
15

As great as the Great Comet of AD 400 undoubtedly was, it pales in comparison to the Great Comet of 6 BC, that is, the Great Christ Comet. The comet of 6 BC was intrinsically and apparently brighter and was larger in coma and tail size than the Comet of AD 400.

Good Viewing Opportunities

With regard to viewing opportunities, the general rule is that cometary apparitions should occur in the evening and in the northern hemisphere to be regarded as great. It should be qualified that, in the ancient world, rather more people would be expected to be awake in the hour or two before dawn than in the modern world. Nevertheless, as now, so then, a comet would have been more widely observed in the evening hours. The ideal time for a comet to be on show is the early part of a night when the Moon is not very bright. At the same time, comets are best seen against the backdrop of a dark sky, meaning earlier mornings or later evenings.

The Bethlehem Star was visible for a long time, but, like most comets, it saved its most magnificent display for the weeks before and after perihelion.

Prior to perihelion it put on a stunning
show as it made its way across the sky from Pisces to Virgo. Much of that glorious procession occurred in the evening and early-night sky when most people were out and about and liable to notice anything unusual in the skies. Among other things, we have suggested that they might have perceived the comet to be Aquarius's water-jar and the water coming out of it, to be an arrow fired from the Archer's bow flying through the sky to slay the Scorpion in August, and to be a trumpet and bright “evening star” in September. For the latter part of its procession it may well have been visible during the daytime.

The comet as a whole, taking the form of a spectacular scepter, began to rise heliacally around the time of perihelion. Two or three days later, at the point when the coma heliacally rose in the eastern sky, it beamed with the brightness of the full Moon, or greater, looking like a baby in Virgo's belly. It was an extraordinarily “bright morning star.” At that time the comet would also have been a dramatic daytime object. Over the following days the comet moved to a higher altitude before the Sun rose, so that it could be seen in a darker sky, although the growth in the comet's size would have diluted the intensity of its brightness. The comet climaxed its apparition in the eastern sky on October 20. At that time the coma looked like a newborn baby and the comet as a whole like a massive iron scepter stretching across the whole sky and resting on the ground in the west. Over the following days it would have appeared very large, long, and bright as it made its close pass by Earth.

Then the comet shifted to the west of Earth and hence the focus of the majestic show moved from the morning sky to the evening and night sky, and from the eastern sky to the western sky. The comet's long-tailed appearances dominated the skies for at least another 30–40 days. At that time, as on its procession to the Sun, the celestial visitor to the inner solar system made its presence abundantly clear to everyone.

Extraordinary Productivity

Regarding productivity, the Christ Comet was very active, beginning its degassing farther from the Sun than any other comet on record, including Hale-Bopp. Moreover, it remained in view from the point at which it was first observed, at least 9½ months before perihelion,
16
until 2 or more months after it.
17
As mentioned above, the hyperactivity of the comet is reminiscent of Hale-Bopp, which pumped out dust and gas like a locomotive, becoming visible to the naked eye almost 10½ months before rounding the Sun. Hale-Bopp maintained naked-eye visibility for 18 months. That was double the time that the previous record-holder, the Great Comet of 1811, had remained observable to the naked eye (9 months, becoming visible 5 months before perihelion), and that comet had been a long way in front of the next in line.
18
We do not know how long in total the Christ Comet remained visible to the naked eye, but it is likely that it at least rivaled Hale-Bopp, and, quite possibly, surpassed it. Hale-Bopp was first observed by the naked eye at magnitude +6.7, because Terry Lovejoy knew exactly where to look, thanks to published data and telescopic and binocular aid.
19
Needless to say, the Christ Comet lacked this advantage and would have been first observed only when considerably brighter (approximately +3.4). Of course, the Bethlehem Star Comet's productivity is why its coma and tail were so large and bright immediately before and after perihelion.

A Long Tail

With respect to the criterion that a great comet must have a tail at least 10 degrees in length, the Christ Comet excels.
20
We have seen that calculations suggest that the comet tail was majestically long, longer than most of Yeomans's great comets, in the western sky prior to perihelion. In addition, of course, after perihelion, on October 20, 6 BC, it seems to have sported an impressively long tail that caused the comet as a whole to look like an iron scepter that stretched from the eastern horizon to the western.
21
The tail would have continued to stretch across the entire dome of the sky for a few days after this. Moreover, its long tail streamed across much of the evening/night sky for the 28–37 days that the Magi were journeying from Bab­ylon to Jerusalem, seeming to go before them to the west. Then one night, between November 23/24 and November 30/December 1, after ushering the Magi to Bethlehem in the south-southwest, the comet stood over the house where Jesus was, about 33–38 degrees in length.

The longest tail lengths among Yeomans's great comets are Tebbutt's Comet of 1861, which grew to 120 degrees, and the Great comet of 1618 (C/1618 W1), which was 104 degrees long. In regards to tail length, the Great Christ Comet seems to have surpassed even these impressive comets.

The Christ Comet's tail is reminiscent of the Great March Comet of 1843. On March 1, 1843, that comet was 30 degrees long, by March 4 it was between 69 and 90 degrees, on March 21 about 64 degrees, and on March 30 approximately 38 degrees.
22
Such a sustained period of tail length is most impressive. However, it is outdone by the Christ Comet, for its tail was longer and remained so for a considerably greater time. Nevertheless, if one wants to get a good idea of what the Christ Comet looked like as it processed from Pisces to Virgo or as the Magi journeyed westward to Judea and then found the house in Bethlehem, one can do little better than look at images of the Great March Comet of 1843.
23
See figs. 5.27–28; 6.6, 10; 10.16.