96 Recent Advances in Stellar Astronomy
stars are of the same order of magnitude. Those in giant
stars are smaller, but are usually measurable in thousands
of tons per square inch, even when the density cannot be
many times greater than that of air. To withstand such
a pressure, at this density, the gas must have a temperature
of many millions of degrees.
What can we say of the properties which matter would
exhibit at these temperatures? Twenty years ago, the
only answer would have been, “Very little”; but now, with
our knowledge of atomic structure, we can say a good deal.
The extreme violence of the collisions between the atoms
would knock off all the electrons of the outer shells, and
keep them off. The lighter atoms—perhaps as far as
sodium or even beyond—would lose all their electrons, and
be reduced to bare nuclei. The heavier ones would retain
their innermost one or two rings or shells of electrons, but
lose the outer ones, which contain a considerable majority
of the whole number of electrons originally present. We
can be certain, however, that the nuclei themselves would
emerge quite unscathed from these collisions, and that if
an isolated nucleus, or the battered fragment of a heavier
atom, had a brief interval of relative quiet, it would begin
to pick up electrons again from those which passed by
slowly enough, and to reconstitute the atomic structure.
Could we remove a portion of the matter in this strange
state and let it cool, the familiar atoms would thereupon
rebuild themselves, bit by bit, and at the end they would
be the same as ever.
The principal differences at the high temperature, from
our present standpoint are : first, there would be a vast
multitude of free electrons flying about, as well as the
far heavier atomic nuclei, so that the average “molecular
weight”—in determining which every free-moving particle