protosun

protosun

[′prōd·ō‚sən]
(astronomy)
The condensation of material that lay at the center of the solar nebula and accreted material from it to form the sun.
References in periodicals archive ?
The moment the protosun and protoplanets were beginning to take their final forms into the solar system you see today, the sun ignited and gave off a huge blast of solar wind.
[X.sub.r] represents the fraction of material that is refractory and F represents the fraction of mass that does not accrete onto the protosun. The choice 0.01 is a maximum for F and corresponds to all the mass which comprises the planets falling from the accretion flow.
We assume an increase in ancient particle fluxes over the current particle flux of ~4 x [10.sup.5], yielding an energetic particle flux of 3.7 x [10.sup.12] protons [cm.sup.-2] [s.sup.-1] for F > 10 MeV at the surface of the protosun.
A possible scenario is that the irradiation of target material occurred in a volatile rich region away from the protosun. This region would contain much more target materials, that is, Cl, S, and K.
These coalesced to form a central core, the putative protosun. As it grew it swept the inner parts of the nebula clean.
Thus the disk's angular momentum must be redistributed outward, which allows the inner-disk material to join the protosun while outlying matter is spun to greater radii.
Once the accumulating disk achieves a mass roughly one-third that of the protosun, it becomes gravitationally unstable and changes from an elegant, symmetric item of cosmic dinnerware to something less regular, perhaps resembling a miniature galaxy.
They also formed coatings of complex organic compounds and mantles of frozen ices on more refractory grains, though the ices would have evaporated when the grains were warmed as they fell toward the protosun.