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 DISNEY: Well, the first thing we did was to apply for some observing time, which much to our amazement we got a little bit of: thus, 3 or 4 nights on a rather small telescope—on the 36" telescope at Steward. These types of experiments were usually done by people with colossal telescopes and all sorts of modern equipment. And in fact we would never have got time, I don't think—being complete novices—on a decent large telescope. So it was kind of fortunate for us that we did have a small telescope. So they said, "Oh well, they'll only waste two or three nights on a small telescope anyway." Well, it was very funny, really, because they thought, first of all, it was a huge joke that two theoreticians were going to observe anyway. I mean, it's a kind of stock joke they have in all observatories that anybody who uses a pen and pencil and his brain and mathematics is totally hopeless with his fingers and is bound to put his foot through or his fingers through all the equipment and so on and can't observe. So there were jokes all around the Observatory which we took in fairly good spirit, because we kind of agreed with everybody.
But a couple of things completely changed the whole outlook of what we were doing. First of all, a paper arrived from Australia of an English astronomer out there called Mike Lodge who discovered another pulsar which was near a supernova remnant. Now, it'd been predicted all along that the place you would find a neutron star would be close to or inside a supernova remnant. And more importantly, this new pulsar that Mike Lodge had discovered, was a very, very fast one. It pulsed on and off 11 times a second.
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MORRISON:
That made everyone realize that you couldn't turn a whole star's radio emission
on and off that fast, no matter what you did. And the only answer—and
there was an answer available and everyone began to believe that then—was
that the star that was doing the radio pulsing—that the pulsar must
be a very tiny star indeed. We knew of two small kinds of stars. Let me
call them condensed stars—that's what we tend to call them. There is
a class of star called a white dwarf. White dwarf matter is the most condensed
form of normal matter with nuclei and electrons that we know about. And
if you make a star out of white dwarf matter, the star shrinks down to the
size of a planet a few thousand miles across. And so such a star might somehow
emit pulses maybe a second or a half-second or just possibly a tenth of
a second but hardly very sharp ones that were sharp compared to the tenth
of a second spacing. And so the possibility that a white dwarf was the source
of the pulsars that we heard was still—I think, as I recall it—I
still thought it was an open question, but it didn't look very good.
Because of course there is another kind of matter, and another kind of condensed star that goes with it, and that is what people call a neutron star. It is one big nucleus. The electrons have disappeared entirely or almost entirely, and in their place is nothing but nuclear matter. But not a single nucleus, but nuclei fused together, so you have one nucleus as big—well, as massive as the sun, but of course enormously condensed—little condensed objects as massive as maybe one-half or one-fifth or one-tenth the star they started from. But only as big—no longer as big as a star or as big as a planet—but only as big as a mountain. And of course, spinning, because everything spins. And as you know, as you make something smaller it tends to spin more and more rapidly. And now that thing—you see it only takes light a ten-thousandth of a second to cross that star—and so that can be expected to make quick pulses. |
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