The Stars, Legacy of a Golden Age: Arabic Astronomy

Arabic Astronomy from Baghdad to Cordoba

While Europe was going through the "Middle Ages," the Islamic world experienced an extraordinary scientific boom. Centers of knowledge like Baghdad became beacons of astronomical knowledge.

Between the 8th and 15th centuries, the Arab-Muslim world experienced a scientific golden age. From Baghdad to Cordoba, via Damascus, Cairo, Isfahan, and Samarkand, scholars translated, corrected, and expanded on Greek, Persian, and Indian works. Astronomy was one of the most brilliant fields of this era, which later nourished the European Renaissance. Many star names we still use today—such as Altair, Betelgeuse, or Rigel—as well as the astrolabe (angular measurement instrument used in ancient astronomy), are direct traces of this Arabic heritage.

The Origins and Transmission of Knowledge

After the founding of the House of Wisdom (Bayt al-Ḥikma) in Baghdad in the 9th century, Arab scholars translated the works of Aristotle, Ptolemy (Almagest), and Indian astronomers like Aryabhata. These translations were accompanied by critical and experimental work. Muslims also had practical needs: determining the direction of the qibla (towards Mecca), prayer times, and the dates of the lunar calendar.

Instruments and Observatories

Arab astronomers not only perfected the tools inherited from the Greeks and Persians; they also invented several original instruments and unprecedented calculation methods. Their practical genius transformed astronomy into a science of measurement based on geometry and instrumental precision.

• Universal astrolabe: invention attributed to Al-Zarqali (11th century), capable of functioning for any terrestrial latitude, while Greek models were limited to a specific region.
• Portable astronomical rings: an Arab innovation derived from the armillary sphere, allowing the measurement of celestial heights without a flat map; ancestors of modern surveying instruments.
• Sine quadrant: introduced by Al-Khujandi and perfected in Rayy around the year 994, it used the sine function for the first time to determine the height of the Sun and establish the latitude of a place.
• Jacob's staff (or qadib al-falak): developed in the Islamic world in the 12th century, this sliding rod sighting instrument allowed the measurement of angular distances between two stars; it later inspired the sextant of European navigators.
• Water-powered astronomical clock (mīzān al-zamān): developed by Al-Jazari (13th century), it combined hydraulics and mechanics to indicate the position of the Sun and the duration of the day—a true celestial clock.
• Stereographic astrolabe: perfected by Al-Sufi and Al-Biruni, it was equipped with new engraved plates for different latitudes and highly precise sighting devices (alidade).
• Astronomical tables (Zij): original works such as Al-Khwarizmi's Zij al-Sindhind or Nasir al-Din al-Tusi's Zij-i Ilkhani; they contained numerical models of planetary motion based on systematic observations.
• Permanent observatories: Arab scholars founded the first organized observation centers (Maragha, Damascus, Isfahan, Samarkand), equipped with monumental fixed instruments and teams of astronomers specializing in data reduction.

These concrete innovations show that Arab astronomers went beyond the simple transmission of ancient knowledge: they invented new tools for calculation and observation, foreshadowing the methods of modern astronomy based on experimental measurement.

Legacy of Star Names Full of Meaning

Arab astronomers often gave stars names derived from familiar images or animals. These names, which reflect the linguistic and cultural richness of the medieval Arab world, have survived thanks to star catalogs established by scholars such as Al-Sufi (903-986), author of the famous Book of Fixed Stars.

The translations carried out in Toledo and Palermo in the 12th century enabled the diffusion of Arab knowledge to Latin Europe. The star catalogs of Al-Sufi were integrated into those of Tycho Brahe (1546-1601), and then Johannes Bayer (1572-1625), who gave them Greek designations (Alpha, Beta, etc.).

The IAU (international Astronomical Union) officialized several of these Arabic names during the standardization of star catalogs in 2016. Today, about 60% of named stars retain an appellation of Arabic origin.

N.B.:
Arabic astronomy also introduced lasting technical terms such as azimuth (from "as-sumūt", directions) and nadir (from "naẓīr", opposite). These words respectively designate the horizontal angle and the point opposite the zenith (point in the sky directly above the observer).

FAQ: Everything about Arabic star names