英语翻译
a pulsar is a celestial object that emits llight in short burst a pulsar in the crab nebula flashes at a rate of 30 times/s,suppose the light pulses are caused by the rotation of a spherical object that emits light from a pair of diametrically opposed "flashlights" on its equator.what is the maximum radius of the pulasae if no part of its surface can move faster than the speed of light?