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Text #7692

Yeomans. Comets
[p. 381]

684 September 6; (P = October 2.8, d = 0.26 on September 7) China, Japan.

Comet Halley. On September 6 or 7 a broom star was seen in the west with a tail more than 15 degrees long. It was observed for approximately 33 days.

Ho (258)

Text #2345

Kronk. Cometography: A Catalog of Comets. Series: Cometography. Vol. 1
[pp. 109--111]

1P/684 R1 (Halley)

Discovered: 684 September 6.5 (Δ=0.26 AU, r=0.81 AU, Elong.=36°)

Last seen: 684 October 8.4 (Δ=1.32 AU, r=0.59 AU, Elong.=25°)

Closest to the Earth: 684 September 6 (0.2562 AU)

Calculated path: UMa (Disc), COM (Sep. 6), BOO (Sep. 9), VIR (Sep. 13), SER (Sep. 14), LIB (Sep. 19), SCO (Sep. 29), LIB (Oct. 6)

The spectacular appearance of this comet really shook up the Europeans. According to the Nuremberg Chronicles (1493)** this “hairy star” was blamed for three months of heavy rain and lightning which resulted in the deaths of numerous people and animals, as well as fields of grain being ruined.** In Asia, however, the usual careful astronomical observations were being made.

The astronomical treatise of the Chinese text T’ang hui yao (961) and the astronomical treatise of the Chinese text Hsin T’ang shu (1060) say a “broom star” was first seen on 684 September 6. The T’ang hui yao notes it was located in the northwest while the Hsin T’ang shu claims it was located in the “west in the evening sky.” Either way, the date and location indicate a probable UT of September 6.5. Both sources say the comet was more than 10° long.

The Japanese text Nihongi (720) says a “broom star” was first seen on 684 September 7 The comet “appeared in the northwest” and was more than 10° long. The date and location indicate a UT of September 7.5.

The date of the comet’s final appearance is a matter of debate, with four Chinese sources indicating three different dates. The annals of the Chiu T’ang shu (945) say the comet was seen for 33 days, indicating a final sighting on October 8, and the astronomical treatise of the Hsin T’ang shu seems to be in agreement as it specifically says the comet “disappeared” on October 9. The astronomical treatise of the T’ang hui yao notes that the comet “lasted for 42 days and then disappeared,” which indicates a date of October 17, while the astronomical treatise of the Chiu T’ang shu says the comet was visible for 49 days, or until October 24. Since the orbit of this comet is very well established, an examination of the motion immediately reveals that dates of October 17 and 24 would probably be too late for observations. The comet would have been steadily fading after the perihelion passage in early October and by the 24th it would have set about 15 minutes after the sun. A final appearance date of October 8 would actually fit very well. The comet would have then been in the evening sky, implying a UT of October 8.4.

The comet may also have been observed in Armenia. Ghevond Yeretz wrote History of Armenia sometime during the 8th century. He says that in the first year of the reign of Armenian governor Ashot Bagratuni, “a hairy star of a surprising sight appeared, having a pillar-like shining and was called a comet.” Bagratuni reigned from 685-9.

Andrew Palmer (1993) described a comet or comets seen by Michael the Syrian during 684. He said, “At this time a large comet appeared and stayed for eleven days. … Afterwards a great comet appeared again, every evening for 41 days; then others appeared alongside it for seven days in the month of September.” David Cook (1998) has suggested that the great comet is probably the actual comet seen in 684.

J. Williams (1871) dated the Chinese observations as July 8 and August 10. Ho Peng Yoke (1962) said Williams overlooked the intercalary fifth month of that year in the Chinese calendar.

The first identification of this comet with 1P/Halley was by J. R. Hind (1850), and he said the comet probably passed perihelion in October. Other orbits were later computed by P. H. Cowell and A. C. D. Crommelin (1908), T. Kiang (1972), Yu-Che Chang (1979), D. K. Yeomans and T. Kiang (1981), J. L. Brady (1982), Werner Landgraf (1986), and G. Sitarski (1988).

The Yeomans - Kiang orbit is given below and indicates the comet reached a maximum solar elongation of 73° on August 21, and its greatest declination of +45° (apparent) on September 4. The comet’s solar elongation steadily decreased to a minimum of 30° by September 9 and then increased to a maximum of 39° by September 19. Thereafter, the elongation steadily decreased and the comet passed only 2° from the nun on October 30.

Based on the comet’s observed brightness from September 6 onward, this comet should have been an easy object in the morning sky from mid-August until the first days of September. The declination would have ranged from +26° to +39° and the solar elongation would have ranged from 55° to 73°. It is puzzling that no observations were recorded for this period. In 1985, F. Richard Stephenson and Kevin K. C. Yau suggested this may have been due to overcast weather.

T 684 Oct. 2.767 (UT)
ω 99.149
Ω (2000.0) 43.800
i 163.418
q 0.57958
e 0.96815


Full Moon: August 30, September 29, October 29

Sources: Nihongi, book 2 (720), p. 364; History of Armenia (8th century), p. 127; Chiu T’ang shu (945), p. 170; T’ang hui yao (961), p. 170; Hsin T’ang shu (1060), p. 170; Nuremberg Chronicles (1493), folio 157a; A. G. Pingré (1783), p. 333; MNRAS, 10 (1850 Jan. 11), p. 56; PMJS (Series 3), 36 (1850 Jun.), p. 474; J. Williams (1871), p. 42, MNRAS, 68 (Supp. 1908), pp. 665-70; The Observatory, 33 (1910 Mar.), p. 130; Nihon Temmon Shiryo (1935), p. 477; Hsi Tsê-Tsung (1958), p. 110; Ho Peng Yoke (1962), p. 170; MRAS, 76 (1972), pp. 35, 53; CAA, 3 (1979), p. 122; Scientific American, 240 (1979 May), pp. 160-70; D. K. Yeomans and T. Kiang (1981), p. 643; J. L. Brady (1982), p. 210; JBIS, 38 (1985), p. 205; W. Landgraf (1986), p. 258; G. Sitarski (1988), p. 263; The Observatory, 108 (1988 Aug.), p. 127; Palmer (1993), p. 197; personal correspondence from David Cook (1998).

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