Friday, 30 March 2012

'Abd al Rahman al Sufi & the Andromeda Galaxy.

Al Salamu 'Alaykum.

While reading about the Andromeda (pic above) Galaxy (the nearest neighbor of our own Milky way), I came across this reference to a Muslim astronomer on the net:

In the venerable Star Names: Their Lore and Meaning, Richard Hinckley Allen noted that: "... the Great Nebula, the Queen of the Nebulae, ..., is said to have been known as far back as A.D. 905; was described by [Abd-al-Rahman] Al Sufi as the Little Cloud before 986; and appeared on a Dutch star-map of 1500."

Some details about him:
Abd-al-Rahman Al Sufi (December 7, 903 - May 25, 986 A.C)Abd-al-Rahman Al Sufi ( according to R.H. Allen (1899) - Abd al Rahman Abu al Husain, sometimes referred to as Azophi) was living at the court of the Emir Adud al-Daula in Isfahan (Persia), and working on astronomical studies based on Greek work, especially the Almagest of Ptolemy. He contributed several corrections to Ptolemy's star list, in particular he did own brightness/magnitude estimates which frequently deviated from those in Ptolemy's work. Also, he was the first to attempt to relate the Greek with the traditional arabic star names and constellations, which was difficult as these constellations were completely unrelated and overlapped in a complicated way.
Al Sufi published his famous "Book of Fixed Stars" in 964 (Al Sufi, 964), describing much of his work, both in textual descriptions and pictures. In his descriptions and pictures of Andromeda, he included "A Little Cloud" which is actually the Andromeda Galaxy M31. He mentions it as lying before the mouth of a Big Fish, an Arabic constellation. This "cloud" was apparently commonly known to the Isfahan astronomers, very probably before 905 AD.
In this book, he probably also cataloged the Omicron Velorum cluster IC 2391 as a "nebulous star", and an additional "nebulous object" in Vulpecula, a cluster or asterism now known as Al Sufi's or Brocchi's Cluster, or Collinder 399. Moreover, he mentions the Large Magellanic Cloud as Al Bakr, the White Ox, of the southern Arabs as it is invisible from Northern Arabia because of its southern latitude.
Al Sufi's observations were not known in Europe at the time of the invention of the telescope, so that the Andromeda Nebula M31 was independently rediscovered by Simon Marius in 1612 with a moderate telescope.
The astronomical community has honored Al Sufi by naming a Moon Crater after him; Moon Crater Azophi is at 22.1S, 12.7E and 47.0 km in diameter.

Nebulous Objects in Al Sufi's Book of the Fixed Stars1. [h and Chi Per (NGC 869/884), Ptolemy No. 191]

"The first star [in Perseus] is the little cloud .. situated on the right hand." 2. [M44 (Praesepe, NGC 2632), Ptolemy No. 444]

"The first of the stars [in Cancer] is the little patch which resembles a small cloud surrounded by four stars which are found - with the patch being in the middle - two in fromt and two behind." 3. [M7 (NGC 6475), Ptolemy No. 567]

"The first of the stars external to the figure [of Scorpius] is the nebulosity following the sting; mag 4-5." 4. [Ptolemy No. 577, asterism of Nu1 and Nu2 Sgr]

"The eighth star of Sagittarius is the cloudy star, which is also double, in the eye." 5. [Ptolemy No. 734, asterism of Lambda, Phi1 and Phi2 Ori]

"The first star of the Giant [Orion] is the cloud which is in the head and which is composed of three stars." 6. [Cr 399, including 4 and 5 Vul]

".. a little cloud situated to the north of two stars in the notch of Sagitta." 7. [M31 (Andromeda Galaxy, NGC 224)]

"The Arabs recognize two series of stars surrounding the figure of a large Fish below the throat of the Camel. These stars belong partly to this constellation [Andromeda] and partly to the northern Fish which Ptolemy describes as the twelfth figure of the Zodiac. These two series begin at a little Cloud situated very close to the 14th star which is found at the right side [of And] and which belongs to the three which are above the girdle." 8. [IC 2391 (Omicron Velorum Cluster)]

".. above the 37th star [Delta Navis], at a distance of one cubit, there is a nebulous star."

Schjellerup (1874) identifies No. 6 as "4 and 5 Vul," No. 7 as the Andromeda "Nebula," and assumes No. 8 is John Herschel's h 3140 (NGC 2669), which however is non-existent; IC 2391 was not recognized at that time (1874).

Wa Salamu 'Alaykum.

No comments:

Post a Comment