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Absorption lines - Dark lines that are
produced in a spectrum because intervening
atoms absorbed photons of specific
wavelengths. Angstrom - A unit of measure equal to 10 -12 meters. Astronomy - The branch of science focusing on celestial objects, dealing with their size, location, composition, dynamics, origin, etc. Astrophysics - Investigation, through remote sensing, of the physical principles of astronomical objects. Binary numbers - A system of numbers that has two as its base and can be used for numerical coding of data. Black hole - A body (usually a collapsed star) whose surface gravity is so great that neither matter nor light can escape from it. Charged coupled device (CCD) - An electronic device that consists of a regular array of light sensitive elements that emit electrons when exposed to light. CCDs are used as the light-detecting element in telescopes, television cameras, etc. Concave lens or mirror - A lens or mirror with an inward curvature. Continuous spectrum - A spectrum unbroken by absorption or emission lines. Convex lens or mirror - A lens with an outward curvature. Diffraction - The spreading out of light waves as they pass by the edge of a body or through closely spaced parallel scratches in a diffraction grating.
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Dispersion - Breaking up of light into its
component colors. Doppler shift (effect) - Changes in the wavelengths of sound or light as the distance between the emitter and the receiver changes. Earth-based telescope - Telescope mounted on the surface of Earth. Electromagnetic spectrum - The complete range of all wavelengths of electromagnetic radiation. Enhancement (computer) - Boosting the color or contrast of a faint image through computer processing. Excitation - The state that occurs when electrons are raised by an external input, such as light or an electronic current, to higher energy levels. Fluorescence - A spontaneous emission of a photon of light that occurs when an electron drops down from a higher energy level (See excitation.) to its original level. Frequency - The number of waves that pass a point in one second. Frequency is usually expressed in units of hertz (waves or cycles per second). Gamma rays - Electromagnetic radiation with wavelengths shorter than 10 -12 meters. Geostationary satellite - A satellite placed in an orbit 35,900 kilometers over Earth's equator that remains in the same place at all times. Infrared - Electromagnetic radiation with wavelengths ranging from approximately 10 -4 to 10 -6 meters. Light gathering power (LGP) - The ability of an optical instrument to collect light. |