Knowra Five-hundred-meter Aperture Spherical Telescope Five-hundred-meter Aperture Spherical Telescope The Five-hundred-meter Aperture Spherical Telescope (FAST) is a Chinese radio telescope built in a natural karst depression in Guizhou Province. Its 500-meter spherical reflector directs radio waves to a movable receiver.
Spherical reflector : A curved reflecting surface shaped as part of a sphere. FAST’s 500-meter reflector is spherical rather than a steerable parabolic dish.
Pulsar : A rapidly rotating neutron star whose beams of radiation appear as regular pulses. FAST has discovered many pulsars by detecting their faint periodic radio signals.
Dawodang depression : A natural karst depression in Guizhou, China, that houses the FAST radio telescope. Its shape and scale provided a ready-made basin for FAST’s enormous reflector.
Arecibo Observatory : A former 305-meter radio telescope built in a natural sinkhole in Puerto Rico. Like FAST, Arecibo used a fixed reflector in a natural depression, but had a smaller aperture.
Active surface : A reflector whose surface elements can be adjusted to form a desired shape. FAST reshapes part of its fixed reflector into a parabola for each observation.
Fast radio burst : A brief, intense burst of radio emission originating beyond the Milky Way. FAST monitors these transient signals to investigate their sources and behavior.
Karst topography : Landscape formed as soluble rock dissolves, creating features such as sinkholes, caves, and depressions. Karst processes created the natural basin selected for FAST’s construction.
Green Bank Telescope : A fully steerable 100-meter radio telescope in West Virginia, United States. Its steerable dish contrasts with FAST’s fixed spherical reflector and movable feed system.
Parabolic antenna : A radio antenna that focuses incoming waves using a parabolic reflecting surface. Unlike a conventional steerable parabolic antenna, FAST selects a pointing direction by deforming its spherical surface.
Neutral hydrogen : Hydrogen atoms whose electron and proton spins are aligned or opposed, producing a 21-centimeter radio line. FAST can map hydrogen emission to study gas in the Milky Way and beyond.
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