Vacuum;Space that contains no matter whatsoever.
Van Allen belts;Radiation belts around the Earth at an altitude of between 4000 and 16,000 kilometers, consisting of charged particles. In these areas, charged particles are captured by the atmosphere.
Variable star;Star that varies in its brightness over time.
Variables;Group of various types of stars, that all show distinct changes in brightness.
Viewfinder telescope;Small telescope mounted on a larger one. The viewfinder telescope's large field of view makes it easier to locate objects in the sky.
Viking probes;US probes (Viking 1 and Viking 2), launched in 1975 to explore Mars.
Wavelength;Distance between two wave peaks or troughs.
Weather satellites;Artificial satellites, collecting detailed information on weather development, that is then transmitted to the Earth.
White dwarf;Collapsed star in the final phase of its life.
Wolf-Rayet star;Extremely hot and bright star that spews out huge quantities of matter.