Radial velocity (RV)
They used special math to guess how often and when this companion star, which they call "Object X," goes by.
Technical definition
The method of measuring the Doppler shift in a star's light to infer its velocity and mass.
They used special math to guess how often and when this companion star, which they call "Object X," goes by.
The method of measuring the Doppler shift in a star's light to infer its velocity and mass.