Why and how did a Japanese poet record the Supernova of AD 1054?



1. Introduction

Stars far more massive than the sun end their lives by the supernova explosions, and the Crab Nebula (Messier 1) is one of the remnants of these explosions. The written accounts of the explosion were recorded in Japan, China, and Arab (only briefly), and the date of the explosion was found to be AD 1054. While the account of the supernova of AD 1054 (hereafter SN 1054) in China is found in the official dynasty chronicle, the records in Japan are found in the two sources, Meigetsuki, the diary of a poet-courtier Fujiwara no Teika (or Fujiwara no Sadaie; hereafter Teika; AD 1162- 1241) and Ichidai Yoki, a chronicle compiled privately around 14th century.

Teika was born in a collateral branch of an aristocratic family line, Fujiwara family, and he is the most famous waka poet in Japan. He spent his life in very turbulent age from the end of aristocratic Heian period (AD 794- 1192) to the beginning of Kamakura shogunate period (AD 1192- 1333). But he was respected by both emperor and shogun as a master of waka. Waka consists of only 31 syllables with the pattern of 5-7-5/ 7-7, and haiku with the pattern of 5-7-5 was derived from waka. The life and some waka of Teika are found in Wikipedia: Fujiwara no Teika.

Teika was born in AD 1162, which was over a century after the appearance of SN 1054, and the record of SN 1054 is found in the entry of AD 1230 in his diary, when he was at the age of 69. While his specialty had nothing to do with astronomy, why was he interested in the supernova, and how did he get the record? In this page, I focus on the historical background of the Japanese records of supernovae, rather than the scientific information derived from these records.

A ground-based image of the entire Crab Nebula (left) and a HST image of the central part of the Crab Nebula taken at a single color band (right). Courtesy of Jeff Hester, Paul Scowen, and NASA

2. The account of SN 1054 in Meigetsuki

The diary of Teika is called Meigetsuki, which means the diary of the bright moon, though this name was coined after Teika's death. Many nobles wrote diaries, for diaries of those days were not fully private ones, but written mainly to hand down to their descendants details of cumbersome rules of ceremonies. In Meigetsuki, accounts of supernovae, including SN 1054, are found in the entry for the 11th lunar month of the second year of the Kwanki (Kanki) reign period (December, AD 1230), which was inspired by the newly appeared guest star. Guest stars included supernovae, novae, and comets, and the guest star of that year was a comet.

In the entry of the 8th day of the month (Dec 13), there is a list of past appearances of eight guest stars, out of which three were definitive supernovae (SN 1006 in Lupus, SN 1054 in Taurus, and SN 1181 in Cassiopeia). The original text of Meigetsuki is extant, and in the exhibition of Reizei family (Reizai family is the direct and existent descendant of Teika), held at the Museum of Kyoto in 2002, I had an opportunity to look at the original text of this part of the diary. I was surprised to find that three different character styles were used in the entry of this single day. The differences of fonts of the translation below reflect those of the original text.

Eighth day. There is a frost. Sky is clear. Northern mountains are covered with snow. Wondering about the guest star, I asked Yasutoshi Ason. The reply is as follows. It is very surprising for the star to appear in the dawn and the evening and in the east and the west.

A guest star had appeared in the night. After the first appearance, we can not watch the star in the day before yesterday because of the cloudy weather.
(Skipped)
It is outrageous for the star to appear in the dawn and the evening and in the east and the west.

Past appearances of guest stars
(Skipped: eight appearances are itemized, and SN 1054 is the sixth item)
At the time of 1-3 am after the middle ten-day period of Tenki reign period of Emperor Go-Reizei, second year, fourth [fifth] lunar month, a guest star appeared in the do (du) of Shi (Zui) and Sin (Shen). It was seen in the eastern direction and shined at the star Tenkan (Tianguan). It was as large as Jupiter.
(Skipped)

It is explicitly stated at the beginning of the above quotation that the information was sent from Yasutoshi Ason, about whom I will discuss in the next chapter. In the account of SN 1054, "Fourth lunar month" should be "fifth lunar month", because the guest star could not be seen in the fourth lunar month by the glare of the sun (the middle ten-day period of the fifth month of this year corresponds to June 19-28 in Julian date. Due to the precession (the wobble of the the Earth's rotation axis), the configuration of the sun and constellations on a given date of AD 1054 differs from that on the same date of recent years).

Shi (Zui) and San (Shen) are two of the 28 Chinese lunar lodges, and correspond to the head and the belt of Orion, respectively (Zui and Shen in parentheses are the Chinese pronunciation; Japanese and Chinese share the same Chinese characters, but their pronunciation are somewhat different. In what follows, Chinese pronunciation is added in parentheses.). The star Tenkan (Tianguan) is zeta Tau. See the right image, which is an armillary sphere in Kusyuon-in (Osaka prefecture) made around AD 1700. Constellations are mirror-reversed. Vertical lines show the ranges of each lunar lodge, which are not equal length on the contrary to the western zodiacs. Of course, the position of SN 1054 (M1) is not depicted in this sphere.
Do in the account of SN 1054 literally means "degree", but in this case it can be translated as "in the same right ascension as that of". For details, see Appendix 1.

Among the three character styles used in the entry of this day, the first one is used in the rest of the diary, but two other styles appear only in this part. I asked the museum for details, and Mr. Makoto Dobashi, the curator of the museum, kindly answered my question. According to him, there are few opportunities even for the specialist to inspect the original text before this exhibition. This part seems to have been written at the bureau of Onmyo (Yin-Yang), to which Yasutoshi Ason belonged to, sent to Teika, and pasted into the diary. Diaries of those days were long scroll, assembled by pasting papers. The size of papers was nearly standardized, so letters from other persons could be filed easily.
I speculate that the account of the second style was written by Yasutoshi Ason, and the account of the third style was written by a colleague of Yasutoshi, though Mr. Dobashi did not go so far.
So Teika did not search the record of past supernovae for himself, nor did he even write down the record for himself. The next question is: what was the relationship between Teika and Yasutoshi Ason, the informant of the record of supernovae?

3. Abe no Yasutoshi

The full name of Yasutoshi Ason (Ason is a courtesy title) was Abe no Yasutoshi. He was a public officer of the bureau of Onmyo (Yin-Yang), the charges of which were daily astronomical observation, divinations based on the observation, calendar making, time keeping, and general divination. Comets and guest stars were considered to be bad omens as well as eclipses, shooting stars, occultation, and the close encounters between the planets and fixed stars. And if these celestial phenomena happened, ceremonies were held at Buddhist temples and Shinto (Japanese native religion) shrines, and sometimes even amnesties were proclaimed to prevent upcoming disasters (by the way, the origin of the word "disaster" is dis (bad)+ aster (star)). This notion, as well as culture and art as a whole, was imported from China, where unusual celestial phenomena were considered to be messages from the heaven to warn bad politics.
In Meigetsuki, in entries after a guest star appeared in AD 1230, which led to the account of SN 1054, it was stated that the guest star was very ominous, and people feared it irrespective of social class, offerings were made in thirteen Shinto shrines, and a sutra was recited at Nanden (the southern palace) for the prayer of the guest star.

Abe family, to which Abe no Yasutoshi belonged, specialized in the art of Onmyo (divination), and a practitioner of this art was called Onmyoji (a master of divination). Abe no Seimei, who established his family line as authorities of this art, was a legendary hero, and as a magician, he is as popular as Harry Potter in today's Japan. Even a movie titled Onmyoji, the hero of which was Abe no Seimei, was created (DVD of this movie is sold at Amazon: Onmyoji). Onmyoji was originally a title of a public officer in the bureau of Onmyo, but as the government declined, they began to serve for nobles individually, which led to the relationship between Teika and Yasutoshi.

In Meigetsuki, Yasutoshi appears more than ten times in seven years between AD 1225 and AD 1231. Before this period, Abe no Yasutada, the stepfather of Yasutoshi, served for Teika for nearly 30 years. Below is the summary of the entries in which Yasutoshi appears.

These entries show the actual activities of Onmyoji, and they also show that there was a continuous relationship between Teika and Yasutoshi. Nobles like Teika needed such helps from Onmyoji, and Onmyoji got reward for their services. And it was one of activities of Onmyoji to make a list of past appearances of guest stars, but for what?

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Right picture is a scenery of Sagano in the western Kyoto, where a second residence of Teika stood. Now, Sagano is a popular sightseeing spot in Kyoto. The bridge in the picture is called Togetsu-kyo, which means the moon-crossing bridge. While the bridge was constructed before the age of Teika, the present name of the bridge was coined after Teika's death.

4. Comet lists and Guest star lists

The report from Yasutoshi to Teika was not the unique case of the list of past appearances of comets and guest stars (hereafter comet list and guest star list, respectively). In Taiheiki, a historical epic written in the 14th century, it is stated that a comet and a guest star (actually a comet) appeared at the same time in AD 1362. A court astrologer report to an emperor that "the first guest star (in Japan) appeared when Moriya oppressed Buddhism (Moriya is a name of a noble in 6th century, who supported Shinto, Japanese native religion). Until now, guest stars appeared 14 times. Of these, two times were good omens, and twelve times were very ominous ones. Comets appeared 86 times since the tyranny and fall of Iruka (a name of a noble in 7th century), and there is no case where bad disaster did not followed." And the comet of AD 1362 was connected with earthquakes, famine, and rebels at that time.
Also in Meigetsuki, it is stated that only the guest star of AD 1006 (a supernova) was followed by no disasters and only birth of a prince, and Teika wrote that "it might be a most fortunate and sacred reign."

When unusual celestial phenomena appeared, a court astrologer, who was included in Onmyoji in a broader sense, was supposed to report to an emperor the divination of the phenomena. Officially, these reports were confidential to prevent conspiracies and rebels inspired by the divinations. But as the government declined, some of these reports leaked out like this description in Taiheiki, the guest star list in Meigetsuki, and the items below.

Individual examples were not mentioned in Taiheiki, but some lists of individual comets appeared in diaries and documents written near the same age as Teika. For example, the record of the comet of AD 1060, which appeared six years later than SN 1054, appears in five documents (there is no contemporary record of the comet of AD 1060, as well as SN 1054), which are itemized below.

Except for Ichidai Yoki, the account of the comet of AD 1060 appears as one item in the comet lists, which were written when a new comet appeared (I speculated that the record in Ichidai Yoki was also based on a comet list. For details, see Appendix 2.). These lists were written to foretell the future by consulting precedents.

Guest stars appeared less frequently than comets (according to Taiheiki, 14 times and 86 times, respectively), so guest star lists were distributed less frequently, for comets and guest stars were considered as different objects, and the comet lists and guest star lists were written separately. This may be the reason why records of the comet of AD 1060 are more extant than those of guest star of SN 1054 (two records: Meigetsuki and Ichidai Yoki). The original record in the bureau of Onmyo, on which these lists were based, existed at least until the middle of the 14th century (see Taiheiki), but might be lost in the subsequent fire or turmoil. It was fortunate that some comets were classified as guest stars (for unknown reason; sometimes there were disputes among Onmyoji on whether newly appeared object was a comet or a guest star) like the one which appeared in AD 1230, which lead to the account of SN 1054 in Meigetsuki.

5. The legacy of Teika

Teika's interest in comets and guest stars had nothing to do with his specialty of waka poem. But his fame of waka helped the preservation of his documents, including Meigetsuki. Reizei family, direct descendants of Teika, has survived as authorities of waka until the present day. They worshiped Teika and Shunzei (father of Teika, and he is also a famous waka poet), and preserved their documents carefully for over 700 years, and Meigetsuki is designated as a national treasure.

The residence of Reizei family, which was built at AD 1790, is known as the oldest extant aristocratic residence. The residence was opened temporarily in the autumn of 2005. Below are the photos taken at that time.

Even today, Meigetsuki and other documents are preserved in the white storehouse (right picture), which was restored recently, in the residence.

Both Onmyoji and Teika were not interested in supernovae in a modern sense of astronomy. They feared comets and guest stars as bad omens, and tried to foretell the future by consulting past events following these objects. And Teika could get the guest star list through the daily relationship with Onmyoji, Abe no Yasutoshi. But whatever their intention was, they observed the supernovae and preserved their records, which today's Japanese can be proud of.

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References
Japanese
Imagawa Fumio, "Kundoku Meigetsuki (Meigetsuki in the Japanese reading)"; the original text of Meigetsuki was written in Chinese.
Imagawa Fumio, "Meigetsuki Jinmei Jiten (Dictionary of names which appears in Meigetsuki)"
Kanda Shigeru, "Nihon Tenmon Shiryo (Astronomical records in Japanese historical documents)"
Saito Kokuji, "Teika Meigetsuki no Tenmon Kiroku (Astronomical records in Meigetsuki)"

English
Stephenson and Green, "Historical Supernovae and their Remnants"

2000.5.8 Japanese version 1.0
2006.6.12 English version 1.0
2007.1.11 English vsrsion 1.0.1
Copyright(C) 2000-2007, USUI Tadashi, All Rights Reserved


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