Article ID: CBB931216833

Tycho Brahe, Abū Maʿshar, and the comet beyond Venus (ninth century A.D.) (2016)


From his observations of the a.d. 1572 supernova and the a.d. 1577 comet, Tycho Brahe concluded that such transient celestial objects are outside the Earth’s atmosphere, and he quoted the ninth century a.d. Persian astrologer and astronomer Abū Macshar: Dixit Albumasar, Cometa supra Venerem visus fuit; i.e., the latter had reported much earlier that comets were seen beyond Venus. However, even from a more detailed Latin translation, the observations and logic behind Abū Macshar’s conclusion were not understandable. We present here the original Arabic text (manuscript Ankara, Saib 199) together with our translation and interpretation: Abū Macshar reported that he had observed Venus in (or projected onto) the tail of a comet and concluded that the comet was behind Venus because he had observed the extinction of Venus due to the cometary tail to be negligible (light of Venus was unimpaired). He then concluded that the comet would be located behind Venus. He also mentioned that others had observed Jupiter and Saturn in cometary tails, so that those comets would even be located beyond those two outer planets – in the sphere of the stars. The dates of the observed close conjunctions were not mentioned; using known orbital elements for a few comets, we found a few close conjunctions between comets and planets from a.d. 770 to 868, but we cannot be sure regarding which conjunctions were reported. While the argument of Abū Macshar is not correct (as cometary tails are optically thin), the conclusion – namely that comets are outside the Earth’s atmosphere and beyond the moon – is correct. This may have helped Tycho Brahe to come to his revolutionary conclusion.

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Authors & Contributors
Jardine, Nicholas
Tybjerg, Karin
Mosley, Adam J.
Levy, David
Wallach-Levy, Wendee
Swerdlow, Noel M.
Journal for the History of Astronomy
Archive for History of Exact Sciences
Centaurus: International Magazine of the History of Mathematics, Science, and Technology
Social Research
Endeavour: Review of the Progress of Science
Tarikh-e Elm (The Iranian Journal for the History of Science)
Prometheus Books
Johns Hopkins University Press
Les Belles Lettres
Cambridge University Press
Arab/Islamic world, civilization and culture
Cross-cultural comparison
Comets; meteors; meteorites
Brahe, Tycho
Kepler, Johannes
Ursus, Nicolas Reimarus
Copernicus, Nicolaus
Rheticus, Georg Joachim
Osiander, Andreas
Time Periods
16th century
17th century
15th century
14th century
Mediterranean region
Eastern Europe

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