Palomar color image of the Crab Nebula M1. The bright reddish filaments of hot excited gas form a chaotic web superimposed over the blueishly glowing diffuse background of high-energy electrons which emit synchtotron radiation as they get accelerated by the extremely strong magnetic field filling the space within the nebula. This magnetic field is generated by the rapidly rotating neutron star which formerly was the core of the pre-supernova star and is now the Crab pulsar.
This photo was generated to visualize the polarisation of the synchrotron radiation from the Crab Nebula. It was created from four photographic plates taken on the Palomar 5m telescope, using a filter which excludes the emission lines from the gaseous filaments, and thus allowing only the synchrotron light to pass through. Each of the four images was taken with a polarisation filter, filtering out light with a certain direction of linear polarization. Between exposing the images, this filter was 45 degrees (i.e., 0 deg, 45, 90, and 135). The four plates were colored as explained below, and superimposed to generate this impressive image, which shows a surprising symmetry of the source of the synchrotron radiation, i.e. the strong magnetic field filling the space in the nebula.
Technically, to obtain this images, one of the four plates was contact copied to make a positive, and this positive was used to extract a difference image from the other three plates. These three difference images were used as the red, green and blue channels to make a colour negative, which made the color image shown. All the work was done photographically. These colours would not be visible through a telescope, even with polarisation filters, since they are representative of something that cannot be seen.
See also: Malin and Pasachoff, Discovering the Color of the Crab Nebula in the July, 1993 edition of Sky and Telescope (86 :1 43-46)
The images in this page are copyrighted and may be used for private purpose only. For any other kind of use, including internet mirroring and storing on CD-ROM, please contact the Photo Permissions Department of the Anglo Australian Observatory.
Paul Scowen has also provided a Palomar image of M1
Last Modification: 2 Jun 2000, 11:10 MET