Astronomy and Astrophysics - An Introductory Survey, A lecture series by Prof. G. Srinivasan - Lecture 33 - Celestial Masers

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. -------------------------------------------------------------------------------- A maser, like a laser, is a source of bright electromagnetic radiation but in the microwave regime. When microwave radiation is incident upon molecules present in space, sometimes the molecules respond by amplifying it, by producing a 'maser'. Naturally-occurring masers are found near stars and supermassive black holes, as well as in the atmospheres of Jupiter and other Solar System objects. In the most dramatic cases, a water vapor maser can radiate more energy at a single wavelength than does the Sun over its entire visible spectrum. ABOUT THE LECTURE In a historic paper published in 1917, Einstein introduced the concept of “stimulated emission of radiation” by atoms and molecules. The first MASER (Microwave Amplification by Stimulated Emission of Radiation) based on this idea was made in 1953, and the first LASER was made in 1960. After the advent of millimeter-wave astronomy, astronomers discovered a wide variety of MASERS in celestial bodies. In this lecture, we systematically develop the concept of two-level systems in quantum mechanics and stimulated emission from them. Then we discuss the Ammonia MASER and Hydrogen MASER, in terms of two-level quantum systems. 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 readings 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