Question

Given that the rest wavelength means the wavelength measured in the laboratory (where the low point would be expected), what can be said about the red and blue data lines shown?

How is the assumption that the laws of physics are the same everywhere in the Universe relevant here?

Why does this suggest a binary star system?

Answer 1

Answer:

The red line indicates Doppler downshift in frequency (or Redshift) which implies that the object is moving away from the observer measuring the signal. The blue line indicates the Doppler upshift in frequency (Blueshift) which means that the object is here moving towards the observer.

The laws of physics are same everywhere is indicated by the fact that Doppler effect which can be measured here on Earth by moving cars or other small bodies is also consistent with large celestial bodies.

The system here is a binary one because a rotating binary system will exhibit a Doppler shift in the measured frequencies and this is evident in the data as the red and blue lines are about the central rest wavelength. Also, this effect is independent of the rest wavelength and this is evident in the entire spectrum.