Short History of Radio Astronomy Jansky – January 1932 Modified Bruce Array: Harald Friis design December 1932 Jansky’s 1932 Data Grote Reber- 1937 9.5 m Parabolic Reflector! Strip Chart output From Strip Chart to Contour Plot… 1940 Ap. J. paper…barely Reber’s 160 MHz contour map published in the ApJ in 1944. This shows the northern sky in equatorial coordinates. The Reber’s 160 MHz contour map published in the ApJ in 1944. This shows the northern sky in equatorial coordinates. The Reber’s 160 MHz contour map published in the ApJ in 1944. This shows the northern sky in equatorial coordinates. The Reber’s 160 MHz contour map published in the ApJ in 1944. This shows the northern sky in equatorial coordinates. The Jan Oort & Hendrik van de Hulst Lieden Observatory 1944 Predicted HI Line Detection of Hydrogen Line …… Ewen & Purcell 21 cm HI Line (1420 MHz) Purcell HI Receiver: Doc Ewen (1951) Milky Way in Optical Origin of SETI Nature, 1959 Philip Morrison 1959 Project Ozma: April 6, 1960 Tau Ceti & Epsilon Eridani Cosmic Background: Penzias & Wilson 1965 • 20 ft Echo Horn (Sugar Scoop): • Harald Friis design Pulsars: Bell and Hewish 1967 Detection of Pulsars: ~100ft of chart/day Chart recording of the pulsar Examples of scintillating detection and an interference signal somewhat later in time. Fast chart recording of pulsar emission (LGM nomenclature is “Little Green Arecibo Message: 1974 Big Ear Radio Telescope OSU Wow! Signal, Aug. 15, 1977 Sagitarius, Chi Sagittari star group NRAO 36ft Kitt Peak Telescope The Drake Equation The Drake equation states that: where: N = the number of civilizations in our galaxy with which communication might be possible; and R* = the average rate of star formation per year in our galaxy fp = the fraction of those stars that have planets ne = the average number of planets that can potentially support life per star that has planets fℓ = the fraction of the above that actually go on to develop life at some point fi = the fraction of the above that actually go on to develop intelligent life fc = the fraction of civilizations that develop a technology and desire to communicate. L = the length of time for which such civilizations release detectable signals into space .