Chapter 2

Like planets, stars rotate on their axes. Also like planets, they commonly generate magnetic fields, which control the direction and intensity of certain types of radiation they emit.

Mostly none of this is terribly important, inasmuch as in most celestial bodies the two nodes—the magnetic poles and the surface points of the axis—are widely separated. Earth's north magnetic pole, for example, lies beneath Canada's Hudson Bay, several hundred miles distant from the "true" (geophysical) north pole. Indeed, there's fossil evidence that at one point our world's magnetic polarization passed through what's now Africa's Sahara Desert.

Very occasionally, however, the two poles will coincide. That is, the "north" and "south" magnetic poles (actually positive and negative; electromagnetism isn't directional in the way of compass points) will happen to fall exactly where a celestial body's north and south rotational poles are to be found.

That's still pretty inconsequential when the body in question is a planet or a moon of a planet, etc. The existence of the magnetic field is what matters, the polarity is of little importance.

It's not even terribly meaningful when it comes to an ordinary star. After all, a star is no more than a planet grown so large that its own gravity is sufficient to crush the elements that make up its mass tightly enough to begin fusing their atoms, thereby "igniting" itself. In the ordinary course of events the coincidence of the two poles may have minor effects on its energy emissions, but not so significant as to warrant much notice.

Most of the life cycle of any star is spent in the fusion of hydrogen atoms into atoms of helium. As the star ages, though, the available hydrogen is gradually consumed, the star's size diminishes, pressure and hence temperatures rise, and it's now the helium atoms that are being fused together. With increasing rapidity the cycle runs to carbon, oxygen, silicon, each being produced by fusion of atoms of lighter elements, and finally to iron.

At this juncture the progression comes to an abrupt, and usually spectacular, halt. To this stage the process of atomic fusion has produced positive energy (albeit in ever-diminishing quantities). Iron, however, is so naturally dense that the fusion that creates it actually consumes more energy than it generates.

And the star explodes, in an unimaginably immense final blast of energy.

These last throes of its death will instantly consume the entire stellar system—every planet, moon, asteroid, comet, or anything else orbiting around the unfortunate star. Even other stars within a comparatively short interstellar distance—say two or three light-years or so—will feel the radiation severely.

More distant—several light-years or more away—the effects of the explosion will ordinarily be dissipated. Any observers at such a distance will of course notice the sudden increment in the light emitted by the star, by many orders of magnitude (as Chen had done); but the destructive force of the accompanying radiation will have been so diluted across the unfathomable span that it will have no, or at most minimal, impact when it reaches them.

A disproportionate amount of that energy will have been channeled along the lines of the star's magnetic field. For the typical star this will be of only minor interest to an observer beyond its zone of influence; even if the focused emanations from the star's magnetic poles happen to fall on them their impact, due to the star's rotation, will be so fleeting as to carry no destructive effect. Just as a living creature can pass directly through fire without taking harm, provided only that the passage is rapid enough, so will a fast-moving flame passing that same living creature by leave it likewise unscathed.

Unless the star's magnetic and geographic poles coincide. As, by happenstance, was the case with the nova Chen had witnessed.

Had Earth been squarely in line with one of the star's poles it would have been the last sight of his life. A mere ninety-three light years would not have sufficed to protect either him or his planet, both of which would have perished in the immense conflagration that took place all those years ago.

But Earth wasn't in that line, wasn't exposed to either of the exploding star's poles. Probably nothing was; the collimated beam of destruction emanating from the poles was so narrow that little short of a direct targeting would endanger anything more than a very few light-years away. The likelihood of anything else in widely dispersed galactic space lying directly in that tiny range was seemingly infinitesimal.

Probably.