A binary star system consists of two stars that revolve about their centre of mass in circular orbits. Suppose that the system is observed edge on. Because of Doppler shift the spectral lines from the two stars (known as a spectroscopic binary system) are observed to shift periodically about a mean to shorter and longer wavelengths as each star moves towards or away from the observer. a) Explain how the orbital period Porb and components of velocity along the line of sight v0,1 and v0,2, for each star, can be found from the observed spectral lines. b) Explain how the velocities of the two stars, v1 and v2, and the angular velocity of the stars ω can be determined.

A binary star system consists of two stars that revolve about their centre of mass in circular orbits. Suppose that the system is observed edge on. Because of Doppler shift the spectral lines from the two stars (known as a spectroscopic binary system) are observed to shift periodically about a mean to shorter and longer wavelengths as each star moves towards or away from the observer. a) Explain how the orbital period Porb and components of velocity along the line of sight v0,1 and v0,2, for each star, can be found from the observed spectral lines. b) Explain how the velocities of the two stars, v1 and v2, and the angular velocity of the stars ω can be determined.