A spacecraft is in a circular orbit around a distant neutron star. The spacecraf

Question

A spacecraft is in a circular orbit around a distant neutron star. The spacecraft signals Earth when it is at position A. It is designed to operate at a frequency of 109 MHz, but the signal is observed to reach Earth with a frequency of 141 Mhz. (a) The rocket is going Counter-Clockwise around the star. (b) What is the speed to the rocket? ______ m/s (c ) What is the frequency observed at Earth when the rocket is at position C? ________ MHz. (d) What is the frequency observed at Earth when the rocket is at position B or D? ____ MHz. Comment: There are also effects from the general relativity (gravity) in this problem, but we are ignoring these.

Explanation / Answer

f = sqrt( (1 + beta)/(1 - beta)) f0

141 = sqrt( (1 + beta)/(1 - beta))109

beta = 0.252

so v = 0.252*3.0E8= 7.56E7 m/s

c)

now beta = -0.252

f = sqrt( (1-0.252)/(1 + 0.252))*109= 84.3 MHz

d) since motion is perp to earth direction f doesnt change

so 109 MHz

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