ABŪ JAʿFAR MOḤAMMAD B. AL-ḤASAN AL-ḴĀZEN AL-ḴORĀSĀNĪ, astronomer (ca. 287/900-probably 360/970). According to Ebn al-Nadīm (Fehrest, pp. 138, 250) and Ebn al-Qefṭī (Taʾrīḵ al-ḥokamāʾ, ed. J. Lippert, Leipzig, 1903, p. 40), a commentary on the beginning of Aristotle’s De caelo was dedicated to him by Kendī’s pupil, Abū Zayd Balḵī (d. 322/934). And according to Abū Naṣr Manṣūr b. ʿErāq (Rasāʾel, Hyderabad [Deccan], 1947, p. 45), he had correspondence with Ebrāhīm b. Senān (d. 946).

A native of Khorasan (Fehrest, p. 266), Ḵāzen was one of the many eminent scientists who flocked to the various courts of the Buyid dynasts. On 13 Rabīʿ II 348/24 June 959 and 10 Šawwāl 348/15 December 959 he was present at observations of the summer and winter solstices made by Abu’l-Fażl Aḥmad Heravī (Bīrūnī, Taḥdīd al-amāken, ed. P. Bulgakov, Cairo, 1964, pp. 98-99; tr. J. Ali, Beirut, 1967, pp. 67-68; comm. E. S. Kennedy, Beirut, 1973, p. 41). He himself seems to have made an observation of the solar declination at the request of Abu’l-Fażl Moḥammad b. al-ʿAmīd (q.v.), Rokn-al-dawla’s vizier. This took place at Kāšān on 10 Šaʿbān 349/6 October 960 (ibid., ed., pp. 119-20; tr., p. 86; comm., pp. 54-55). Ḵāzen reported the observation in his Zīǰ al-ṣafāʾeḥ, which was composed for the vizier.

Ḵāzen’s writings, as presently known, are as follows. Ebn al-Nadīm (Fehrest, p. 282) and Ebn al-Qefṭī (Ḥokamāʾ, p. 396) list only nos. 1 and 9, although the former does refer to his commentary on Euclid’s Elements (Fehrest, p. 266). 1. Zīǰ al-ṣafāʾeḥ (“Astronomical tables of the timpans”), lost (see E. S. Kennedy, A Survey of Islamic Astronomical Tables, Philadelphia, 1956, p. 137, no. X200). It is cited frequently by Bīrūnī. For example, its concentric model for solar motion is discussed in Āṯār al-bāqīa (p. 259; Chronology, p. 249); Taḥdīd (ed. pp. 57-58; tr., p. 28; comm., p. 12); Transits (ed. as item 3 in his Rasāʾel, Hyderabad [Deccan], 1949, pp. 77-78; tr. E. S. Kennedy, Beirut, 1959, pp. 85-86; note that Abū Jaʿfar’s criticism of Abū Maʿšar’s solar theory occurs in ed., p. 77, tr., p. 85); and al-Qānūn al-Masʿūdī (Hyderabad [Deccan], 1954-56, pp. 630-32). For this theory, see Samsó, “Solar Model.” The theory of trepidation in the Zīǰ also is mentioned by Bīrūnī (Āṯār al-bāqīa, p. 326; Chronology, p. 322). Abū Naṣr (see above) wrote for Bīrūnī a Resāla fī taṣḥīḥ mā waqaʿa le-Abī Jaʿfar al-Ḵāzen men al-sahw fī Zīǰ al-ṣafāʾeḥ (“Epistle on correcting what happened to Abū Jaʿfar because of negligence in the Zīǰ al-ṣafāʾeḥ”). This text is published as treatise 3 in Abū Naṣr’s Rasāʾel (see also Bīrūnī, Resāla fī fehrest kotob Moḥammad b. Zakarīyāʾ al-Rāzī, ed. P. Kraus, Paris, 1936, p. 44). For other references to the Zīǰ, see Samsó, “Solar Model,” and Sezgin, GAS V, pp. 298-99; VI, pp. 189-90. 2. Ketāb tafsīr ṣadr al-maqālāt al-ʿāšera men ketāb Oqlīdes (“Commentary on the beginning of the tenth book of the Book of Euclid”), preserved in many manuscripts (see list in Sezgin, op. cit.). 3. Ketāb al-tafsīr le’l-Maǰesṭī (“Commentary on the Almagest”), lost. Bīrūnī quotes it as reporting observations of the solstices made by the Banū Mūsā (Taḥdīd, ed., p. 95; tr., p. 64; comm., p. 40) and as recording the lengths of the seasons determined by Ḵāled Marvarrūḏī, ʿAlī b. ʿĪsā Ḥarrānī, and Sanad b. ʿAlī (Qānūn, p. 653). Naṣīr-al-dīn Ṭūsī also quotes it (Ketāb al-šakl al-qeṭāʿ: A. Carathéodory, Traité du quadrilatère, Constantinople, 1981, ed., p. 123; tr., p. 259). 4. Ketāb al-borhān ʿalā al-šakl al-sābeʿ men ketāb Banī Mūsā (“Book of the proof of the seventh figure from the Book of the Banū Mūsā”); for a manuscript, see Sezgin, GAS V, p. 299. The work is on Heron’s theorem on the area of a triangle; Abū Jaʿfar’s proof is repeated by Ṭūsī (Rasāʾel, Hyderabad [Deccan], 1939-40, II/1, pp. 26-27). 5. Ketāb al-madḵal al-kabīr elā ʿelm al-noǰūm (“Book of the great introduction to the science of the stars”), lost. Bīrūnī cites it for its methods of determining the weekday on which the month of Moḥarram will begin in any given year (Āṯār al-bāqīa, pp. 202-03; Chronology, pp. 183-84). Perhaps a similar passage in his Qānūn (p. 1232) is from the same source. 6. Ketāb fi’l-abʿād wa’l-aǰrām (“Book on the distances and sizes [of the stars]”), lost; Bīrūnī cites it (Qānūn, p. 1312). 7. Ketāb al-oṣūl al-handasīya (“Book of the elements of geometry”), lost; Abū Naṣr cites it as containing criticisms of Menelaus (Rasāʾel, p. 3). 8. Ketāb fī mayl al-aǰzāʾ (“Book on the declination of the degrees [of the ecliptic]”), lost but quoted by Ṭūsī (Šakl, ed., pp. 115-16; tr., pp. 149-51). 9. Ketāb al-masāʾel al-ʿadadīya (“Book of questions concerning numbers”), lost.

Abū Jaʿfar’s use of conic sections is mentioned by ʿOmar Ḵayyāmī (Resāla fī barāhīn al-ǰabr wa’l-moqābala: F. Woepcke, L’Algebre d’Omar Alkhayyāmī, Paris, 1851, ed., p. 2, tr., p. 3). Ebn Ḵaldūn quotes his view concerning the latitudinal limits of the seven climata (The Muqaddimah, tr. F. Rosenthal, London, 1958, I, p. 115).


See also Y. Dold-Samplonius in Dictionary of Scientific Biography VII, New York, 1973, pp. 334-35.

A. Sayili, The Observatory in Islam, Ankara, 1960, pp. 103-04.

J. Samsó, “A Homocentric Solar Model by Abū Jaʿfar al-Khāzin,” JHAS 1, 1977, pp. 268-75.

Idem, “al-Khāzin,” EI2 IV, pp. 1182-83.

(D. Pingree)

Originally Published: December 15, 1983

Last Updated: July 19, 2011

This article is available in print.
Vol. I, Fasc. 3, pp. 326-327

Cite this entry:

D. Pingree, “ABŪ JAʿFAR ḴĀZEN,” Encyclopædia Iranica, I/3, pp. 326-327; an updated version is available online at http://www.iranicaonline.org/articles/abu-jafar-mohammad-b (accessed on 30 January 2014).