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04-07-2006
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4 July 1054: death of a star, birth of a mystery

Submitter: Richard Strom
Description: "On a ji-chou day in the fifth month of the first year of the Zhi-He reign period a 'guest star' appeared at the SE of Tian-Guan, measuring several inches. After more than a year it faded away." (Ho Peng Yoke, Vistas in Astronomy, 5, 184; translated from the "Songshi") [Chinese text in figure beginning below lower left corner of Crab Nebula image.]
The supernova of AD 1054 was first observed at the Song Dynasty capital, Kaifeng, on July 4. The explosion created the nebula famously named after a crustacean. The association of the Crab Nebula with SN 1054 was firmly established in the mid-twentieth century.
This year marks the 50th anniversary of the publication of a classical paper by J.H. Oort and T. Walraven, "Polarization and composition of the Crab Nebula" (BAN, XII, 285, 1956), which both measured the distribution of linear polarization from the continuum emission, and made a detailed analysis using the still-new synchrotron theory. The photograph uses 'vectors' to show the magnetic field direction and degree of polarization. The observations were made using a photomultiplier tube provided by Dr. Lallemand (Paris Observatory) and a polaroid filter, on the Leiden Observatory 33 cm photographic telescope. (It is remarkable to think that pioneering observations could be made from the center of a city like Leiden in the mid-1950s!) The observations established synchrotron emission as the light source of the blue, diffuse component, and as the emitting electrons have a lifetime of several hundred years, led the authors to argue that there must be continuous injection of energy from near the nebula's center. The results of the paper helped establish synchrotron emission as the primary mechanism for producing radio emission from both galactic and extragalactic sources.
Copyright: Bulletin of the Astronomical Institutes of the Netherlands
 
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