The long-term motion of comet Halley

New Astronomical References in Two Catalonian Late Medieval Documents

“…This day, in the night and some days before and after, it was seen in the sky a star or a comet in the way that is drawn below 19 , with a long tail, and it came out from the part of Ponent (W) and had the rays towards Llevant (E); May God give us good signs. This description, that also appears similarly in the Llibre, where an illustration is included (See figure 10), corresponds to comet C/1468 SI which, according to Yeomans and Kiang (1981) was first detected the 18 September 1468 and then remained visible for 56 days, the date of the Perigee was on 2 October 1468 and reached the maximum brightness the same day with 1-2 magnitude. (See figure 11 for the apparent trajectory of this comet) This year two comets were seen and they were recorded in the chronicles of Gustinsky (6976) (Vyssotsky, 1949) with only a succinct reference:…”

“…The comet was undoubtedly a sign of bad luck. This is a description of C/1471 Y1 which, according to Yeomans and Kiang (1981), was first detected on 25 December 1471 and then it was visible for 59 days, its perigee was on 23 January 1472 being the minimum distance to the Earth 0.07 AU and reaching magnitude -3. The text points out that the comet was first visible in the East and then, some days after, in the west.…”

“…These fragments contain two beautiful descriptions of comet 1P/1456 K1, which is best known as Halley comet (See Figure 7). According to Yeomans (1981), the first report of the comet visible as a naked eye object was on 26 May 1456 and then remained visible for 44 days, the date of the perigee was on 9 June 1456, the minimum distance to the Earth was reached on 19 June 1456 and it was 0.45 AU, it reached its maximum brightness on 19 June 1456 with 0 magnitude. It was bad weather in Barcelona until the beginning of June, as it is written in the input of 1 June, being this maybe an explanation of why the comet was not detected before:…”

“…See figure 12 for the apparent trajectory of the comet. 20 Note of the authors: Picture not included Its computed orbital parameters are in table 7 (Yeomans and Kiang (1981)):  Translation: Sunday the 28th. This day, at midday and already some days before and after at different times, a lot of people saw a big star with a large tail of fire that casted much smoke behind it, from the parts of Ponent (W) and going to Llevant (E).…”

Resonant behavior of comet Halley and the Orionid stream

“…There are no credible observations relating to this comet before 240 B.C. Furthermore, comet Halley has reliably determined (Yeomans and Kiang 1981) perihelion passage times (the first calculations performed by Halley [1705] using Newton [1687]) and orbital elements back till 1404 B.C., beyond which the uncertainty in the orbit starts to increase because of a significant close encounter with Earth at a distance of about 0.04 AU.…”