Glossary of astronomy - W

Weak-line star is a reference to the faintness of the spectral lines for a star compared to standard stars with the same stellar classification. Since most absorption lines are caused by elements other than hydrogen and helium—what astronomers refer to as "metals"—these are sometimes called metal weak stars.[21]

White dwarf is a type of stellar remnant composed mostly of electron-degenerate matter. A white dwarf lacks the mass needed to continue the nuclear fusion process with its constituent atoms, so the object's energy output normally comes from radiative cooling. (But see nova and Type Ia supernova.)

Wilson-Bappu Effect is a correlation between the width of the singly-ionized calcium K-line (Ca II K) at 3933 Å and the absolute visual magnitude of the emitting late-type stars. This linear relation makes it useful for determining the distances of G, K, and M-type stars.[22]