93 light years away in the Perseus constellation, precision radio astronomy has traced out an extended plasma filament from the polar region of the smaller of two of the stars in the Algol group. If you examine the NRAO image carefully http://www.nrao.edu/pr/2010/algol/ (which unfortunately adds an artist's depiction of the two stars to the RF isophote image from the huge international Precision Array image) you can see that the filamentary area is an extended "blob" which narrows and bends down toward the larger star of this close pair. From the image it is not possible to tell if this is a stellar jet which emerges from the plane of the image and bends over and down toward the other star, out of their mutual orbital plane, or if it has been ejected more equatorially and has little out-of-plane motion.
No matter; the mechanisms and formulas for radio frequency radiation from stars have been available since they were published, in Hannes Alfvén's Cosmic Plasma in 1981 and in Anthony Peratt's textbook, Physics of the Plasma Universe, in 1992. In Chapter 6 on Synchrotron Radiation, Peratt writes
[Note for the newer reader - "relativistic" is a term relating the speed of an electron relative to that of light in a vacuum - the faster the electron, the more kinetic energy it carries (in electron volts, eV) and the more "relativistic" it is said to be.]There are other mechanisms of considerable importance operating in the radio region. In particular there are non-coherent and coherent mechanisms connected with the existence of sufficiently dense plasmas which are responsible for radiation derived from plasma radiations, such as the sporadic solar radio emissions. This radiation cannot be attributed to the motion of individual electrons in a vacuum but is due to the collective motion of electrons at the plasma frequency [ = 9 x SQR( number of electrons per cubic meter) in Hertz, or cycles per second (6.1) ]
When a plasma is subjected to a magnetic field [such as around a star! -JJ] there is yet another mechanism which plays an extremely important role in radio astronomy...essentially three types of spectra are observed...cyclotron emission or magnetobremsstrahlung (for) nonrelativisitic or mildly relativistic electron energies (and) synchrotron radiation is reserved for highly relativistic electrons because it was first observed in 1948 in electron synchrotrons. [here on Earth].
Synchrotron radiation was first brought to the attention of astronomers by Hannes Alfvén and N. Herlofsen (1950), a remarkable suggestion at a time when plasma and magnetic fields were thought to have little, if anything, to do in a cosmos filled with "island" universes (galaxies.
Plasmas and their electromagnetic dynamics scale up and down, linking us to our thoughts, to the Sun, to the stars and to the galaxies of stars.
