Physics
Scientific paper
Jan 1944
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1944phrv...65...20g&link_type=abstract
Physical Review, vol. 65, Issue 1-2, pp. 20-32
Physics
3
Scientific paper
By use of the method of successive homology transformations in conjunction with Bialobjeski-Eddington's formula, it is possible to predict the changes of radii and luminosities of massive stars in different stages of their hydrogen and contractive evolution. It is shown that at a certain stage of contraction the star must reach the maximum of its luminosity, and it is calculated that for the star masses of 5, 10, 20, and 40 suns the maximum luminosities are 1×105, 4×105, 1×106, and 4×106 suns, respectively. In the later contractive stages total luminosity of the star remains constant whereas its visual luminosity rapidly deceases because of the shift of energy into the ultraviolet part of the spectrum. It is to be expected that for such high values of the (luminosity)/(mass) ratio, radiation pressure becomes strong enough to eject stellar atmospheres into the surrounding space, and it is shown that the ejection will actually take place if the force of gravity on the stellar surface will be somewhat reduced by the centrifugal force due to axial rotation. It is also shown that under the conditions existing in the ejective atmospheres of Wolf-Rayet stars, radiation pressure is primarily due to the light scattering by free electrons. In discussing the motion of the ejected gases, it may be necessary to assume that their original velocity of about 2000 km/sec. can be considerably reduced by the gravitational action of the star. If this is the case, gaseous envelopes which will form around Wolf-Rayet stars in the course of several centuries will possess properties very similar to those of the planetary nebulae. This would indicate a close evolutionary relationship between these two classes of celestial objects. An alternative evolutionary road of a massive star consists in the formation of an energy-producing shell, which will take place in all cases where the convective currents due to axial rotation are not fast enough to secure homogeneity of stellar matter. It is indicated that the growth of such shells will probably lead to the formation of an extensive atmosphere which offers certain possibilities for the interpretation of the so-called red giant stars as intermediate evolutionary stages between the stars of the main sequence and the Wolf-Rayet stars. In conclusion the problem of stellar collapse, which is expected to take place towards the end of contractive evolution, is discussed in some detail.
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