153P/Ikeya-Zhang and the comet of Hevelius

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153P/Ikeya-Zhang and the comet of Hevelius

• Mark R. Kidger
• Instituto de Astrofísica de Canarias

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Why is 153P/Ikeya-Zhang important?

• Before Comet Ikeya-Zhang the longest confirmed
  2-return comet period was 35P/Herschel-Rigollet.
• 155 years
• Observed in 1788 and 1939
• 153P/Ikeya-Zhang has been the first confirmed
  case of a multi-return comet with Pgt200yrs. It
  may be many years before there is another.
• The 1661-2002 linkage is secure.
• There are proposed linkages to previous comets.
• But there are some major unresolved problems with
  all of the previous known and suspected
  apparitions.

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The comet of Hevelius (C/1661 C1)

• Discovered on February 3rd 1661 in the morning
  sky with a 6º tail.
• The comet was not discovered by Hevelius, but he
  carried out a study of it.
• It faded rapidly and was last seen on March 28th.
• Shortly after discovery Hevelius estimated it as
  fainter than Altair (around magnitude 1-1.5?)
• It is assumed that his last observation on March
  28th was made with the naked eye with the comet
  just visible.
• Hevelius mentions multiple nuclei (unlikely) and
  a rapid decrease in condensation (plausible,
  because the DC decreased rapidly after perihelion
  in 2002).

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Previous identifications

• There has been a great effort to find previous
  apparitions of Ikeya-Zhang given that it is a
  bright comet of quite short period.
• Comets are found by Nakano by Waddington in 877
  and/or 1273 that are possible previous
  apparitions.

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The comet(s?) of 1273

• Hos comet catalogue lists a broom star seen by
  the Japanese (Feb. 5) in the evening sky and the
  Koreans (Feb. 17) in the morning sky.
• The Chinese saw a bluish white guest star with
  the appearance of loose cotton in Auriga on Apr.
  9th.
• Ho lists the two as identical (Ho 439), although
  their position and movement seems incompatible
  with this.
• Nakano links the former with 153P/Ikeya-Zhang (T
  1273 Feb. 4.8) based on the evening-morning
  shift.

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The comet(s?) of 1273

• Waddington shows that the track of the Chinese
  comet is close to that of 153P.
• Over 21 days it moved from the asterism
  28/?/?/?/15 UMa through the bowl of the Plough to
  disappear near Arcturus (evening ? morning sky).
• The perihelion date is tightly constrained by
  these observations
• T1273 Mar. 27.5?1 day
• The latest orbit solution from 1661-2002 gives T
  1272 Dec. 15?5 days with the known
  non-gravitational terms.

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The comet(?) of 877

• The Japanese record a Guest Star in Pegasus that
  appeared on February 11th (Ho 307).
• A comet was observed in the west from Europe for
  15 days in March and a comet in China in June
  July (Pingré 349)
• A Guest Star (ko-hsing) was usually a nova,
  especially if no movement was recorded. A comet
  was a hui-hsing if tailed and a po-hsing if
  not.
• Nakano links the Japanese and European
  observations with 153P.

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The comet(?) of 877

• Yeomans states that the European comet was seen
  in Libra, in the south-west in the morning sky.
• Nakanos linkage puts the comet in eastern
  Cygnus, in the eastern sky at dawn!
• Theoretically it was just visible at magnitude 3
  at this time in the north-west at sunset from
  northern Europe, but very low in a very bright
  sky.
• It looks very unlikely that it would have been
  observed in the evening sky, but would have been
  easy at dawn.

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A Joker in the Pack C/1532 R1

• Edmond Halley noticed that the orbits of C/1532
  R1 and C/1661 C1 are also very similar.
• Initially the preferred identification of C/2002
  C1 was C/1532 R1.

C/1532 R1 C/1661 C1 C/2002 C1
T 1532 Oct. 18.8 1661 Jan. 27.4 2002 Mar. 18.9
q 0.51922 0.442722 0.507200
w 24º.53 33º.450 34º.5777
W 93º.81 86º.562 93º.4156
e 1.0 1.0 0.991207
i 32º.59 33º.015 28º.1110
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The 1661 mystery
Date Comet Mag. Sun Moon
31/12/1660 14º 3.0 -17º New
05/01/1661 15º 2.6 -16º Crescent
20/01/1661 12º 0.7 -14º Waning
23/01/1661 9º 0.4 -13º Last 1/4

• 1661 was a very favourable apparition the best
  of the 4 returns.
• The comet should have had excellent evening
  visibility before perihelion, but was NOT
  observed.

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Why did Hevelius not see it before?

• Hevelius would have had two chances to discover
  the comet pre-perihelion in the evening sky if it
  was as bright as we believe
• In late December-early January around New Moon at
  magnitude 2.5-3 in a dark sky.
• After the January 15th Full Moon around magnitude
  0.5 in twilight.
• Even assuming widespread bad weather, if the
  comet was as bright as thought it would have been
  seen by someone before perihelion.

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Two alternative explanations

• An outburst at perihelion
• It is a common phenomenon in comets often
  associated with sudden aspect changes
• Heveliuss observations of multiple nuclei
• But
• Heveliuss observations are not really credible.
  He could not even resolve Saturns rings clearly!
• John Bortle suggested (2002, TA, 35, 298) that
  Hevelius did not see the comet because of a
  perihelion asymmetry.
• But
• Not really seen in Ikeya-Zhangs light curve.

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Perihelion asymmetry
If we assume that n was constant after
perihelion...
Post-perihelion m0 increases slowly to peak at
m05.4 at T90days. Too little, too late to
explain Heveliuss observations.
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The two comets of 1273 are completely
incompatible. Could the Japanese/Korean date of
observation be a transcription error, as in the
4BC Star of Bethlehem event?
Chinese data
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Given the Nakano linkage 877 and 1273 were rather
poor apparitions. In 877 Comet Ikeya-Zhang would
not have passed m13.5 and in 1273 m12.9.
Waddingtons 1273 linkage is even worse!!!
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Which linkage is correct?

• Nakano uses the doubtful Japanese observation in
  Pegasus in 877 to fix the 877 perihelion passage
  and works forward to 1273.
• Waddington uses the detailed Chinese observations
  from 1273.
• The observational evidence makes the Waddington
  linkage appear more plausible.
• The European observations in 877 and the Chinese
  data from 1273 are difficult to fit to Nakanos
  linkage.

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How bright was the comet of 1273?

• The Chinese observation of colour suggests that
  the comet was very bright.
• If the Waddington linkage is correct the comet
  would have been magnitude 1.5 and fading at
  discovery, even if it was as bright as Heveliuss
  comet.
• Probably too faint to show colour!!
• We must assume that it was even brighter in 1273
  than in 1661.

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How to make sense of all this?

• There is evidence of a systematic fade 1273 ?
  1661 ? 2002.
• What if C/1532 R1 and 153P/Ikeya-Zhang are
  fragments of a single comet that split in the 1st
  Century AD?
• The very bright (m0 1.8) comet of 1532 would be
  the principal nucleus.
• The descending node of 153P is close to Jupiters
  orbit and permits very close encounters. A
  post-split encounter with Jupiter could separate
  the nuclei.

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• This scenario explains the similarity of orbits
  between C/1532 R1 and 153P.
• As a secondary (and much smaller nucleus) a
  systematic fade with time would be expected.
• There are many possible scenarios, but one would
  have a splitting during an apparition in 58AD,
  followed by an encounter with Jupiter in 458AD
  that separated the fragments in T.

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A prediction

• If the splitting scenario is correct, C/1532 R1
  should return around the end of this century.
• Prepare for a potentially very bright comet with
  an orbit similar to Ikeya-Zhang!!