Doppler détermination of orbital v and T
Star (and companion planet) will both orbit the common COM
Observe star spectral line from Earth.
Measure Doppler shift in spectral line.
Max wavelength corresponds to star moving away from Earth. Min wavelength corresponds to star moving towards Earth.
Doppler shift (∆lambda) – at max or min - can be used to determine orbital speed (v)
Orbital period is determined from one cycle of Doppler shift e.g. from one max to the next max.
Dark matter
X detect by any sort of em radiation but whose existence we infer from its gravitational effect
Radial velocity (Vrad)
The component of a star’s v along our line of sight relative to us on earth
Calc by Doppler eqn
Kepler 2nd
The area swiped by an orbital body by a line drawn between the star and planet should be same in the same period of time
Is red shift increasing or decreasing wavelength?
Increase
