Astronomy and Astrophysics - An Introductory Survey, A lecture series by Prof. G. Srinivasan - Lecture 26 - Radio Galaxies

Radio emission was detected for the first time from an external galaxy Cygnus A and the suggestion that it could be a 'double radio source' compelled the radio astronomers to find ways of attaining very high angular resolution of celestial radio sources. This led to the discovery of the "Aperture Synthesis" telescope by Sir Martin Ryle, for which he was awarded the Nobel Prize in 1974 (first Nobel in Astronomy, along with Anthony Hewish). The Giant Meterwave Radio Telescope (near Pune) is the largest among such telescopes in the low-frequency regime. Nowadays GMRT is routinely used for observing Radio Galaxies, sometimes revealing interesting morphologies where the energetic jets emitted by these galaxies twist, wrap, overlap and bend. ABOUT THE LECTURE Radio emission from an external galaxy was first detected around 1950 from the powerful galaxy Cygnus A. There was a suggestion that it was a `double radio source'. This discovery catalyzed the quest for achieving higher angular resolution. This led to the discovery of "Aperture Synthesis" telescopes. Sir Martin Ryle in Cambridge was awarded the Nobel Prize for this discovery. Observations with high angular resolution revealed a remarkable morphology of `Radio Galaxies'. There was a compact central source, presumed to be a super-massive black hole. There were two relativistic jets of particles emanating from the central source, and two gigantic 'lobes' of radio emission at both ends of the jet. This lecture is intended to be an introduction to the world of giant radio galaxies. Lecture 27: Supermassive Black Holes Lecture 28: The case of the missing neutrinos ABOUT THE LECTURE SERIES This lecture series is organized by the Astronomical Society of India as a part of its Golden Jubilee celebrations. Aimed at undergraduate and graduate students, this series of talks by renowned astrophysicist and teacher, Prof G. Srinivasan, starts from the first principles of Physics and builds up the subject rigorously to the present state of our understanding. Series website: https://astron-soc.in/srini-ana The website hosts a question bank as well as a list of suggested reading for each lecture (prepared by Dr. Sushan Konar) ABOUT THE SPEAKER Professor G. Srinivasan In a research career spanning more than five decades, his interests have spanned many aspects of physics and astrophysics. He is a passionate teacher and has authored two outstanding Astronomy texts titled ‘What Are The Stars?’ and ‘Can Stars Find Peace?’ He is a Past President of the Astronomical Society of India, and a Past President of the Division on Space and High Energy Astrophysics of the International Astronomical Union. In his distinguished career he has worked at the University of Chicago, USA; the IBM Research Laboratory in Zurich, Switzerland; Chalmers University of Technology, Goteborg, Sweden; the Cavendish Laboratory, University of Cambridge, England and the Raman Research Institute, Bengaluru Follow us on social media at https://twitter.com/asipoec https://www.facebook.com/asi.poec/ This series is also supported by the IAU OAE Centre in India https://twitter.com/astro4edu_India https://www.facebook.com/OAE-Center-India-105698322030674