C / -43 K1 (Comet Caesar)

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C / -43 K1 (Comet Caesar) [i]
Augusto, denario con stella cometa a otto raggi.JPG
Properties of the orbit ( animation )
Period:  23 May -43 ( JD 1,705,496.5)
Orbit type parabolic
Numerical eccentricity 1.0
Perihelion 0.22 AU
Inclination of the orbit plane 110 °
Perihelion May 25 -43
Orbital velocity in the perihelion 90 km / s
Date of discovery 44 BC Chr.
Older name sidus Iulium , Caesaris astrum
Source: Unless otherwise stated, the data comes from JPL Small-Body Database Browser . Please also note the note on comet articles .

C / -43 K1 (Comet Caesar) , also known in antiquity as sidus Iulium and Caesaris astrum , the star of the deified Julius Caesar , was a comet that appeared in 44 BC. Chr. For seven days at the northeastern sky of Rome appeared. Some sources (e.g. Servius ) mention visibility in the daytime sky .

The comet appeared on the games played by Caesar's adopted son Octavian between July 20 and 23 for Venus as Victoria Caesaris. Therefore the people thought they recognized the deified soul of Caesar in him. Octavian, who at this time had already adopted the name Gaius Julius Caesar and initially apparently intended to refer the sidus to himself, then had this comet attached to the statue of Divus Iulius above the forehead. The sidus Iulium with the inscription divus Iulius also appeared on numerous coins . The name of the comet as sidus Iulium goes back to an ode by the poet Horace from the year 24 BC. BC back.


C / -43 K1: Comet rise in the northeastern sky ( Roman Forum , July 23rd -43, 4:40 pm - 11:40 pm local time)

After Julius Caesar's death on March 15, 44 BC. One of the most celebrated comets of antiquity appeared in the sky over Rome. Roman and Greek sources report details strikingly similar to those reported on a comet seen in China and Korea that same year . The earliest mention of the comet comes from Augustus, Caesar's successor and first emperor of Rome.

Reports by Pliny and Seneca

Denarius with the Sidus Iulium
Temple in honor of Divus Iulius

However, the oldest text with details of the celestial appearance is not found until 77 AD in the Naturalis historia by Pliny :

“Only in one place on earth, namely in Rome, is a comet venerated in a temple because the Divus Augustus declared it to be a very favorable sign for himself. He appeared at the beginning of his reign during the games that he held in honor of Venus Genetrix shortly after the death of his father Caesar in the college still appointed by him. He expressed his joy at this with the following words: 'Just on the days of my games a hair star was seen for seven days in the northern part of the sky; it rose at the eleventh hour of the day, was very luminous and visible in all countries. The people believed that this star indicated the acceptance of Caesar's soul among the immortal gods; for this sake this zodiac sign was attached to the image of his head, which was later consecrated in the forum. ' So he spoke out in public; inside, however, he was delightedly convinced that the star had risen for him and that it would rise with him - and if we want to tell the truth, for the good of the world. "

The Roman historian Suetonius described Augustus' account in similar terms in his De vita Caesarum (120 AD).

The Roman philosopher Lucius Annaeus Seneca wrote his Naturales quaestiones around 63 and reported on a comet that "came out after the death of the deified Julius, during the games of Venus Genetrix around the eleventh hour of the day." Further mentions of the comet were made by Calpurnius Siculus in Eclogues I (60), Plutarch in Bíoi parálleloi (100), Cassius Dio in Roman History (229), Iulius Obsequens in Liber de prodigiis (4th century) and Servius in his commentaries on Virgil's Eclogues and Aeneid during the 4th century . Century. Servius stated three days for visibility and in particular mentioned visibility during the day .

The exact date of the events in Rome was uncertain until recently. It was mentioned that the comet was seen "during the games of Venus Genetrix". The Temple of Venus Genetrix was consecrated on September 26th −45, but two years after its inauguration a new ceremony was created, called the ludi Victoriae Caesaris , which took place around September 20-23. July took place, and the games of Venus Genetrix were combined with these games. As a result, Caesar's comet was probably seen at the end of July −43 (July 44 BC).

Sightings in China

There are also sources reporting that the comet was sighted in China. Bān Gù was the main author of the Hàn Shū (100). In the annals he reports of a "broom star" that was seen in the summer −43 between May 18th and June 16th. He also gives astronomical details on this phenomenon, such as a tail length of 8 to 10 degrees . A Korean report may not be original but is based on Chinese sources.

A recent research report concludes that the Chinese and Roman comets were one and the same, and the authors were able to deduce orbital elements that match both observations. They concluded that the comet was a relatively bright object when it was seen in China, then it faded and could not be seen for a month. Then there was a dramatic outburst of brightness, which at the end of July made it again an object for observation with the naked eye .

Another possibility why the comet was only seen in China in May / June and not before July in Rome is a historically documented eruption of Mount Etna in the same year.


For the comet Caesar only a parabolic orbit could be determined due to the uncertain observation data, which is inclined by around 110 ° to the ecliptic . It thus runs in the opposite direction (retrograde) like the planets through its orbit. At the point of the orbit closest to the Sun ( perihelion ), which the comet traversed on May 25 −43, it was located about 33 million km from the Sun within the orbit of Mercury . A day later he passed Venus at a distance of about 90 million km . Already on May 12th and again on August 1st it came close to the earth to about 1 AU / 150 million km.

Only approximate information from Chinese and Roman observers from an observation period of two months could be used to derive approximate orbit elements , they are therefore subject to great uncertainties, so that only general statements can be made about the orbit of the comet and all figures are given with great care are consider. Using the coarse orbital elements of Ramsey and Light, as given in the NASA JPL Small-Body Database Browser, however, there is a possibility that the comet will still pass close (<1 AU) the planet about eleven months after its perihelion Jupiter experienced what would have massively influenced its orbital elements in any case. The orbit of the comet could have been changed into a long-period elliptical orbit, so that the comet could return to the inner solar system after several 10,000 years .

Chinese sources

  • 班固 (Bān Gù) , (Qián) Hàn-shū (HS) 26: 31b ( Tiān-wén-zhì )
  • 班固 (Bān Gù), (Qián) Hàn-shū (HS) 9 ( Běn-zhì )

Graeco-Roman sources

Secondary literature

  • Christian Bechtold: God and the stars as forms of presence of the dead emperor - apotheosis and cadastre in the political communication of the Roman imperial era and their points of contact in Hellenism . V & R Unipress GmbH 2011, ISBN 978-3-89971-685-6
  • Patrizio Domenicucci: Astra Caesarum - Astronomia, astrologia e catasterismo da Cesare a Domiziano Pisa 1996 (Edizioni ETS), ISBN 88-7741-932-6 . Reviews by John T. Ramsey ; by Martin Pozzi
  • John T. Ramsey & A. Lewis Licht: The Comet of 44 BC and Caesar's Funeral Games . Atlanta 1997, ISBN 0-7885-0273-5 . Review by Geoffrey Sumi
  • K. Scott: "The Sidus Iulium and the Apotheosis of Caesar" . Classical Philology 39 . 1941, pp. 257-272.
  • Hendrik Wagenvoort: Virgil's fourth eclogue and the Sidus Iulium . Amsterdam 1929, pp. 1-38.
  • Mary Frances Williams: "The Sidus Iulium, the divinity of men, and the Golden Age in Virgil's Aeneid" . Leeds International Classical Studies 2.1 . 2003


When beggars die there are no comets seen; The heavens themselves blaze forth the death of princes. Calpurnia (in William Shakespeare : Julius Caesar . II. Ii. 30-31)

Fulget caesaris astrum (= the emperor's star shines), motto of Rudolf II.

See also

Web links

Individual evidence

  1. ^ Gary W. Kronk : Cometography - A Catalog of Comets, Volume 1. Ancient - 1799 . Cambridge University Press, 1999, ISBN 978-0-521-58504-0 , pp. 22-24.
  2. JT Ramsey, AL Licht: The Comet of 44 BC and Caesar's Funeral Game , Scholars Press, Atlanta, 1997, ISBN 978-0-788-50274-3
  3. ^ DAJ Seargent: The Greatest Comets in History: Broom Stars and Celestial Scimitars . Springer, New York, 2009, ISBN 978-0-387-09512-7 , pp. 71-76.
  4. NASA JPL Small-Body Database Browser: C / -43 K1. Retrieved May 27, 2014 (English).
  5. SOLEX 11.0 A. Vitagliano. Archived from the original on September 18, 2015 ; accessed on May 2, 2014 .