After that supernova explosion and collapse has happened, the object that remains-star heavy, asteroid sized-is a "neutron star." It has been crushed together so violently by its own immense gravitation that the electrons of its atoms are driven into its protons, creating the chargeless particles called neutrons. Its substance is so dense that a cubic inch of it weighs two million tons or so; it is like compressing the hugest of Earth's old supertankers into something the size of a coin. Things do not leave a neutron star easily; with that immense, concentrated mass pulling things down to its surface, escape velocity becomes something like 120,000 miles a second. More than that: its rotational energy has been "compressed," too. The blue-white giant star that used to turn on its axis once a week is now a superheavy asteroid-sized thing that whirls around many times a second.
Chou knew there were observations that he had to make-magnetic, X-ray, infrared, and many others. The magnetometer readings were the most important. Neutron stars have superfluid cores and so, as they rotate, they generate intense magnetic fields-just like the Earth. Not really just like the Earth, though, because the neutro1 star's magnetic field, too, is compressed. It is one trillion times stronger than the Earth's. And as it spins it generates radiation. The radiation can't simply flow out from all parts of the star at once-the lines of magnetic force confine it. It can only escape at the neutron star's north and south magnetic poles.
The magnetic poles of any object aren't necessarily in the same place as its poles of rotation. (The Earth's north magnetic pole is hundreds of miles away from the point where the meridians of longitude meet.) So all the neutron star's radiated energy pours out in a beam, around and around, pointing a little, or sometimes a lot, away from its true rotational poles.
So that was the explanation of the thing Chou was seeing. The cones were the two polar beams from the star that lay between them, north and south, fanning out from its poles. Of course, Chou couldn't see the beams themselves. What he saw were the places
where they illuminated tenuous clouds of gas and dust as they spread out.
