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The eclipsing system of epsilon Aurigae and its possible relevance to the formation of a planetary system


Recent observations of the eclipsing system of ɛ Aurigae converge to a conclusion that its secondary (‘invisible’) component constitutes a flat disc, some 40 AU across, which is semitransparent, of constant optical depth, and dims light non-selecting without a trace of polarization. Its constituent particles must, therefore, be large in comparison with the wavelength of observation — probably greater, on the average, than 10 μ; with no upper limit imposed by the observations. The mass of this disc appears to be no less than 20 ⊙; and its mean temperature, approximately 500K.

The primary component of ɛ Aurigae is an F2 Ia supergiant, probably less than one million years old; while its less massive (and, consequently, less evolved) companion has not yet reached a stellar stage. The external characteristics of this disc-like companion appear to approximate the properties that have frequently been postulated as pre-requisites for the formation of a ‘planetary system’. A hypothesis is put forward that, in the secondary component of ɛ Aurigae, we witness at present, an evolutionary process that may result in the formation of a planetary system very much more massive than our own in the astronomically near future.

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With a possible exception of S Doradus, which according to Gaposchkin (1943) is an eclipsing variable with a period of 40.2 y.

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Kopal, Z. The eclipsing system of epsilon Aurigae and its possible relevance to the formation of a planetary system. Astrophys Space Sci 10, 332–339 (1971).

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  • Evolutionary Process
  • Optical Depth
  • Recent Observation
  • Primary Component
  • Planetary System