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Radio Telescopes ROBOTS Professional Development Workshop PARI School of Galactic Radio Astronomy Discovery of Radio Astronomy • Radio Waves first discovered by Hertz in 1888 • Radio Astronomy born 1931 when Karl Janski first detects extra terrestrial radio waves – Source: Galactic Center • 1937 Grote Reber first modern radio telescope – 1944 Reber publishes first radio map of sky Janski’s First “Radio Telescope” Image courtesy of NRAO/AUI Reception of Radio Waves • Radio waves cause oscillation of free electons in metals. • A radio dish reflects radio waves and focuses the waves to a point • The intensity of radio waves striking the dish is measured as voltage Radio Waves arrive at the dish and are focused to the Receiver. The Receiver converts the radio waves to an electric signal that is amplified and recorded. PARI Formation of 21cm Radio waves (1420 MHz) One source of radio waves from space is hydrogen gas. The hydrogen atom can emit a radio wave with a wavelength of 21 cm or frequency of 1420 MegaHertz.