The Great Christ Comet by Colin Nicholl, Gary W. Kronk

no catalog detailing orbital elements of meteoroid streams or radiants of meteor showers that occurred two millennia ago. Gravitationalfactors mean that orbits evolve and hence the orbital elements of the meteoroid stream then might no longer resemble what they are now (particularly in their argument of perihelion [ ω ] and longitude of the ascending node [ Ω ] values). However, it is still interesting to observe that a few meteoroid streams have orbits that are at least superficially similar to that of the meteoroid stream responsible for the meteor storm in 6 BC.
    If the meteors radiated from high on the tail and the meteoroid stream orbit had a semi-major axis of 1.04–1.1 AU, it would be reminiscent of the μ and κ Hydrid meteor showers (and the related January Hydrids and Iota Sculptorids) not only in perihelion distance (0.233–0.237 AU compared with 0.215 AU and 0.249 AU respectively for the κ and μ Hydrids) but also in eccentricity (0.77–0.79, compared with 0.79 and 0.77), velocity (33–34 km/second compared with 37.6 and 39.1 km/second), and, to some extent, inclination (48–50 degrees compared with 66.5 and 71.8 degrees). 27
    In addition, it should be noted that within the large population of near-Earth asteroids are an unknown number that are cometary in nature (like Apollo asteroid 4015 Wilson-Harrington = Comet 107P/Wilson-Harrington) or are remnants of comets. It is therefore perhaps worth pointing out that some objects classified as Apollo asteroids have orbits that are similar to possible orbits of the meteoroid stream that caused the Hydrid meteor storm of 6 BC. Of course, we must remember that 2,000 years of orbital evolution may mean that the orbit of the Hydrid meteoroid stream is no longer recognizably similar to the orbits of these asteroids.
    The orbit of Apollo asteroid 2009 HU58 (magnitude 19) is reminiscent of the orbit of the meteoroid stream responsible for the 6 BC meteor storm if the latter’s meteors radiated from one-third of the way from γ Hydrae to HIP59373 ( table 14.3 ).
    Name
q
e
i
ω
Node
Period
2009 HU58
0.187
0.91
35.77
285.35
62.90
2.97 years
Hydrids (Vinf=40)
0.19
0.908
39.3
226.1
51.0
2.97 years
    TABLE 14.3 A comparison of the orbit of asteroid 2009 HU58 to the orbit of the meteoroid stream responsible for the 6 BC Hydrids, assuming that the meteors radiated from one-third of the way from γ Hydrae to HIP59373 and that Vinf=40.
    The orbit of the Apollo asteroid 2000 UR16 (magnitude 23) is reminiscent of the orbit of the meteoroid stream responsible for the 6 BC meteor storm if the latter’s meteors radiated from two-thirds of the way from γ Hydrae to HIP59373 ( table 14.4 ).
    Name
q
e
i
ω
Node
Period
2000 UR16
0.507
0.4388
11.74
228.78
33.85
313.64 days
Hydrids (Vinf=19)
0.501
0.444
13.8
233.7
50.4
312.42 days
    TABLE 14.4 A comparison of the orbit of asteroid 2000 UR16 to the orbit of the meteoroid stream responsible for the 6 BC Hydrids, assuming that the meteors radiated from two-thirds of the way from γ Hydrae to HIP59373 and that Vinf=19.
    The orbit of Apollo asteroid 2004 WK1 (magnitude 21) is reminiscent of the orbit of the meteoroid stream responsible for the 6 BC meteor storm if the latter’s meteors radiated from HIP59373 ( table 14.5 ).
    Name
q
e
i
ω
Node
Period
2004 WK1
0.293
0.73
34.5
223.1
51.85
413.14 days
Hydrids (Vinf=30)
0.274
0.704
36.0
222.0
50.9
325.3 days
    TABLE 14.5 A comparison of the orbit of asteroid 2004 WK1 to the orbit of the meteoroid stream responsible for the 6 BC Hydrids, assuming that the meteors radiated from HIP59373 126 minutes before sunrise and that Vinf=30.
    If the meteoroid stream had a Jupiter-family orbit and its radiant was one-third of the way from γ (Gamma) Hydrae to HIP59373, it would have had a relatively small perihelion distance (q=0.173 AU), although larger than 96P/Machholz 1 (q=0.124 AU). It is interesting to compare the Hydrid meteoroid