A spaceship is traveling from Earth to Epsilon Eridani. Every hour, the spaceship sends a transponder signal back to Earth. At what speed would the spaceship have to be traveling relative to Earth for the transponder signal to have a frequency in the rest frame of Earth that is of the frequency of the signal in the rest frame of the spaceship?
In the spectrum of light coming from a star, the Hα emission line is found to be shifted toward the red end of the spectrum. In the rest frame of the source object, the H line has a frequency of Hz. In the rest frame of Earth, the H line appears at Hz. If all of this redshift is due to relativistic motion of the star relative to Earth, how fast is the star moving away from Earth? Give your answer to 3 significant figures as a multiple of the speed of light.
An emission line in the spectrum of the light from a star is at a frequency of Hz in the rest frame of a laboratory on Earth. The star is moving away from Earth at a speed of . What was the frequency of the emission line in the rest frame of the star? Ignore the effect of cosmological redshift. Give your answer to 3 significant figures.