Vol 10, No 11

On the radiation problem of high mass stars

Golden Gadzirayi Nyambuya


Abstract A massive star is defined as one with mass greater than ~8-10 M⊙. Central to the on-going debate on how these objects [massive stars] come into being is the so-called Radiation Problem. For nearly forty years, it has been argued that the radiation field emanating from massive stars is high enough to cause a global reversal of direct radial in-fall of material onto the nascent star. We argue that only in the case of a non-spinning isolated star does the gravitational field of the nascent star overcome the radiation field. An isolated non-spinning star is a non-spinning star without any circumstellar material around it, and the gravitational field beyond its surface is described exactly by Newton's inverse square law. The supposed fact that massive stars have a gravitational field that is much stronger than their radiation field is drawn from the analysis of an isolated massive star. In this case the gravitational field is much stronger than the radiation field. This conclusion has been erroneously extended to the case of massive stars enshrouded in gas and dust. We find that, for the case of a non spinning gravitating body where we take into consideration the circumstellar material, at ~ 8-10 M⊙, the radiation field will not reverse the radial in-fall of matter, but rather a stalemate between the radiation and gravitational field will be achieved, i.e. the in-fall is halted but not reversed. This picture is very different from the common picture that is projected and accepted in the popular literature where at ~8-10 M⊙, all the circumstellar material, from the surface of the star right up to the edge of the molecular core, is expected to be swept away by the radiation field. We argue that massive stars should be able to start their normal stellar processes if the molecular core from which they form has some rotation, because a rotating core exhibits an Azimuthally Symmetric Gravitational Field which causes there to be an accretion disk and along this equatorial disk. The radiation field cannot be much stronger than the gravitational field, hence this equatorial accretion disk becomes the channel via which the nascent massive star accretes all of its material.


Keywords stars: circumstellar matter — stars: formation — radiative transfer

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