A binary star in which the presence of an unresolved companion is revealed by small oscillations in the movement of the visible component caused by the gravitational influence of the unseen component.
Values in a reference system used to relate the position of a body on the celestial sphere. Four main coordinate systems are utilized in astronomy: the equatorial, horizontal, ecliptic, and galactic c
oordinates systems.
A device whose main function is detection. Any device or array of electronic sensors connected to a computer, used to detect the passage of a particle or photon; e.g. a charge-coupled device (CCD).