The Stark effect is an effect of an electric field on spectral lines: electron orbitals that would normally be degenerate (identical binding energies) are influenced by presence of an electric field so that they differ. The effect is the electric-field analog of the Zeeman effect. The Zeeman effect causes stars to show two or more closely-spaced lines in place of one, but since the plasma surrounding stars is conductive, not much of an electric field is maintained. However the Stark effect does occur from the short-term tiny electric dipoles occurring as charged particles pass close to each other and/or the analogous effects of the electrons of passing neutral atoms. The resulting influence on the photon wavelength is random, based upon the particular circumstance, and rather than producing multiple individual lines, produces some line broadening, termed Stark broadening, one of the mechanisms of pressure broadening; such broadening is increased by the density of the gas or plasma and thus by the pressure.