ASTR 103 - Astronomy

Glossary - Z

Zeeman effect

Splitting or widening of the spectral lines of a radiating source in the presence of a magnetic field. The phenomenon was discovered in the laboratory by Dutch physicist P. Zeeman in 1896.

zenith

Point in the sky that is immediately overhead.

zero-age main sequence (ZAMS)

Principal branch in the H-R diagram reached by stars that have evolved to stability as the result of hydrogen burning.

zero space curvature

Flat space continuum characterized by Euclidean geometry; there is no warping of space as there is in positive or negative curvature.

zodiac

(see also signs of the zodiac).

zodical light

Faint band of light that tapers upward from the horizon, following the course of the ecliptic. It apparently results from the reflection of sunlight by interplanetary dust in the plane of the Solar System.

zone of avoidance

Irregular band along the Milky Way where few or no galaxies appear as a consequence of severe obscuration of light by interstellar dust in or near the Galactic plane.