Astronomy and Astrophysics - An Introductory Survey, A lecture series by Prof. G. Srinivasan - Lecture 32 - The Gamma Ray Universe

AstroPHYSICS with Srini (https://www.youtube.com/@astrophysicswithsrini1094) The newly launched youtube channel of Prof. Srinivasan. WATCH it, SUBSCRIBE to it, and bring it to the attention of your friends! And here is why. The present course of introductory lectures will end with the 41st lecture. There are many topics in basic physics, as well as astrophysics, that you encountered in this course that deserves a 'revisit'. Prof. Srinivasan plans to make new videos on these topics and upload them to this channel. This will start to happen after the last lecture of this series has been released. Meanwhile, this channel is up. Currently, the PLAYLIST contains the 40 lectures that he delivered at the International Centre for Theoretical Sciences, a few years ago. You are welcome to contact Prof. Srinivasan at [email protected] if you have suggestions for topics, or if you have questions. -------------------------------------------------------------------------------- Gamma rays, representing the most energetic part of the electromagnetic spectrum, are produced by the hottest and the most energetic objects in the universe. Because of their extremely small wavelengths, gamma-rays can not be captured and reflected by mirrors, unlike visible light or X-rays. Moreover, gamma-rays coming from space are mostly absorbed by the Earth's atmosphere. So gamma-ray astronomy could not develop until it was possible to get our detectors above all or most of the atmosphere, using balloons or spacecraft. And we finally developed the ability to detect gamma-rays only in the 1960s, opening up a new window to the Universe. ABOUT THE LECTURE One of the new windows to the universe is Gamma Ray Astronomy. This branch of astronomy came of age during the past twenty years. Today, one can detect gamma rays with energies from MeV to TeV. Low-energy gamma rays come from the interstellar medium, supernova remnants, etc. High-energy gamma rays are associated with very energetic sources, such as Pulsars, Quasars, Active Galactic Nuclei, etc. In this lecture, I shall discuss various sources of gamma rays, as well as various emission mechanisms, in particular Compton scattering. 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