What evidence do we have that pulsars are neutron stars?
What will be an ideal response?
Pulsars could not be ordinary stars. A normal star, even a small white dwarf, is much too big to pulse that fast. Nor could a star with a hot spot on its surface spin fast enough to produce the pulses. Even a small white dwarf would fly apart if it spun 30 times a second. The pulses last only about 0.001 second, placing an upper limit on the size of the object producing the pulse. If a white dwarf blinked on and then off in that interval, you would not see a 0.001-second pulse. That's because the point on the white dwarf closest to Earth would be about 6000 km closer to you, and light from that spot would arrive 0.02 s before the light from the bulk of the white dwarf. As a result its short blink would be smeared out into a longer pulse. Only a neutron star is small enough to be a pulsar.
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Fill in the blank(s) with correct word
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