Radio Astronomy Summer School Introduction Early History of Radio Astronomy. Tatsuhiko Hasegawa (ASIAA)

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1 Radio Astronomy Summer School 2008 Introduction Early History of Radio Astronomy Tatsuhiko Hasegawa (ASIAA) 1. Radio astronomy was interferometry from the beginning. 2. Closely related to developments in engineering and society. 3. We need to reduce radio noise and to protect radio frequencies.

2 1870 Maxwell Theory of Electromagnetic Wave Hertz Laboratory Generation and Detection of Radio Electromagnetic Wave. Many scientists attempted to detect Solar radio emission in m-cm bands all failed Planck Theory of Thermal Blackbody Radiation => Solar thermal radiation will be weak in m-cm band. Marconi First long-distance radio communication (across Atlantic ocean) Heaviside and Kennelly Earth ionosphere reflects radio waves. Turned out only freq < 20 M Hz Commercial radio telephone service Jansky discovers cosmic radio wave from Galactic center at 20.5 M Hz Reber builds a radio telescope and maps cosmic radio emission (from Galactic plane) at 162 M Hz Hey, Southworth, Reber (separately) observed Solar radio emission. Radar technology advanced Pawsey (Australia), Ryle (UK) developed interferometry technique. Ryle & Vonberg (Cambridge UK) built a 2-element interferometer and detected Solar flares and Cas A. Bolton & Stanley (Au) used 'Sea interferometry'. 10 compact radio sources were discovered by Ryle, Smith, Elsmore made first catalog of point radio sources (1C catalog, 1949). Antenna movements and use of Earth rotation. Many dipole antennas to form an interferometer (Mills Au). Many small dishes in cross-pattern (Christiansen Au) 1951 First detection of the 21cm line of H I. Ewen & Percell (US). Muller & Oort (D). Pawsey (Au) m (Dutch) m (Harvard) m (UK) m x 2 (Caltech). 26m (US Navy) m (Michigan). 26m (NRAO). 22m (USSR) Discoveries of radio galaxies Parks 64m (Au). 25m x 2 (Melbourne, Au) m (NRAO) m (Arecibo, US) m x 3 (Ryle 1-mile UK) m (Mark II, UK). 36m (Haystack, US) m (GB). 46m (Ca) K cosmic microwave background radiation Discovery of pulsars Nobel prize : Martin Ryle & Antony Hewish for contributions to radio astronomy Nobel prize : Penzias & Wilson for the discovery of cosmic background radiation.

3 Karl Jansky and his rotating antenna in New Jersey (1928). Courtesy of NRAO/AUI. Jansky, working at Bell Telephone Laboratory, investigated the origin of static noise for radio telephone service.

4 Grote Reber's telescope in his backyard in Illinois (1938). Reber was a radio engineer. Courtesy of NRAO.

5 Arno Penzias and Robert Woodrow Wilson (1965) at Bell Laboratory built this radiometer intended for satellite communication and radio astronomy experiments. They encountered an excess antenna temperature of 3.5 K. They could not explain the excess. This led to the discovery of the cosmic microwave background radiation. Courtesy NASA. (

6 NRAO 25.5m #1 (1958) at Green Bank Green Bank 90m telescope (1962) before and after the collapse on Nov 15, 1988.

7 Early Activities in Radio Astronomy in the United Kingdom Courtesy Jodrell Bank Observatory and University of Manchester Parabolic reflecting wires (65 m long) at Jodrell Bank (1947) Jodrell Bank Mark I 75m (1957) First day at Jodrell Bank (1945 Dec)

8 Jocelyn Burnell and the 4.5 acre (135 m x 135 m ) array (U of Cambridge) that was used in the discovery of pulsars (1967). Courtesy University of Manchester. ( ) The facility was intended for Solar radio monitoring. The supervisor was Dr. Hewish.

9 Eight Yagi-antennas (1951) A reflector using a hole in the ground (1953) Early activities in radio astronomy in Australia at WW II radar station. Courtesy ATNF and CSIRO. Two Yagi-antennas (1947) Cygnus-A detection chart by 'sea interferometry' (1948).

10 Modern Radio Telescopes in Australia Courtesy ATNF / CSIRO Compact Array at Narrabi (1988) Parkes 64m and 18m (1963)

11 Early Activities in Radio Astronomy in The Netherlands Courtesy ASTRON Westerbork Observatory HI 21cm line was detected and mapped with this 7.5 m telescope (originally a German military radar dish) in Kootwijk, Holland ( ). Prof. Jan Oort was eager to exploit the radio technique. Dwingeloo 25m (1956) Wsterbork 25m x 12 (E-W) (in 1970)