||A vibration in some media that transfers energy from one place to another. Sound waves are vibrations passing in air. Light waves are vibrations in electromagnetic fields.
||The distance between two wave crests. Radio waves can have lengths of several feet; the wavelengths of X-rays are roughly the size of atoms.
||The force that governs the change of one kind of elementary particle into another. This force is associated with radioactive processes that involve neutrons.
|White Dwarf Star
||The hot, compact remains of a low-mass star like our Sun that has exhausted its sources of fuel for thermonuclear fusion. White dwarf stars are generally about the size of the Earth.
|Wide Field / Planetary Camera (WF/PC)
||A collection of eight separate, yet interconnected, cameras originally used as the main optical instrument on the Hubble Space Telescope. Four cameras were used in tandem to observe in either wide-field, low-resolution mode or narrow-field, high-resolution (‘planetary’) mode. The Wide Field and Planetary Camera 2 replaced the WF/PC during the December 1993 servicing mission.
|Wide Field and Planetary Camera 2 (WFPC2)
||The Hubble Space Telescope’s ‘workhorse’ instrument, WFPC2 snaps high-resolution images of faraway objects. Its 48 filters allow scientists to study precise wavelengths of light and to sense a range of wavelengths from ultraviolet to near-infrared light. The instrument has four CCDs (charge-coupled devices), which collect information from stars and galaxies to make photographs. WFPC2 was installed aboard the Hubble telescope during the December 1993 servicing mission.