Radio astronomy

Radio astronomy studies celestial objects and phenomena by detecting and analyzing radio waves they emit or reflect. It reveals processes that may be obscured or invisible at other wavelengths.

Radio telescope: An instrument that collects and measures radio waves from astronomical sources. Its antennas and receivers turn incoming radio waves into measurable signals.
Cosmic microwave background: The relic thermal radiation from the early universe, now observed mainly at microwave wavelengths. Its radio and microwave measurements test models of the universe's origin and evolution.
Electromagnetic spectrum: The full range of electromagnetic radiation, ordered by frequency or wavelength. Radio astronomy studies one broad region of this spectrum.
Karl Jansky: An American engineer who identified radio emission from the Milky Way in 1933. His detection of a celestial radio source is commonly treated as radio astronomy's beginning.
Optical astronomy: The study of celestial objects using visible light. Optical observations show different emission processes and often resolve sources more sharply with smaller instruments.
Aperture synthesis: An imaging technique that combines signals from separated antennas to produce the resolution of a much larger telescope. It lets radio arrays resolve fine structure without building a single enormous dish.
Pulsar: A rotating neutron star whose beams of radiation produce regularly repeating pulses. Radio pulse timing reveals neutron-star physics and enables precise tests of gravity.
Radio wave: Electromagnetic radiation with frequencies conventionally classified as radio. These waves are the signals collected by radio observatories.
Grote Reber: An American radio engineer who built an early dedicated radio telescope and mapped the sky. His 1937 dish enabled systematic observations after Jansky's discovery.
Infrared astronomy: The study of celestial objects through infrared radiation. Infrared and radio observations probe overlapping cool environments but trace different wavelengths and transitions.

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