Today I attended the second day of the Science Academies’ lecture-workshop on astrophysics. Continuing from yesterday (you can read the update here), Professors G Srinivasan and Biman Nath gave their last lectures for this event. And two new speakers, Prof Uday Shankar, a radio astronomer at the Raman Research Institute and Dr Sreekumar, an ex-NASA scientist now working at ISRO, joined us with their lectures on Radio and X-ray Astrophysics respectively.
From Chandrashekhar to Hawking
Prof Srinivasan began from Chandrashekhar and his first attempt to understand White Dwarfs—or Quantum Stars as they were then called—and his further attempts when he arrived at what we now called the Chandrashekhar Limit. He explored the problems encountered, the concepts of Inverse Beta-Decay, neutron stars, predictions made by theories that came much later and so on, in trying to explain the various possible ends that stars may meet.
For the curious reader, apparently, a quake on a neutron star (owing to its density) will equal roughly 45 on the Richter scale on Earth. This is perhaps sufficient to shift the entire Earth from its orbital position!
Having then reached Einstein’s work, Schwarzchild’s solution of Einstein’s equations and the idea of Black Holes, Prof Srinivasan—who has worked with Roger Penrose and Hawking—spent some time sharing his experiences of those raging times when physicists all over the world—Beckenstein, Carter, Hawking, Israel, Kerr, Penrose and Zeldovich—were trying to figure out how, why and whether Black Holes would radiate.
With this ended his four lectures for this event and he left us having placed on the stage the current obstacles standing in the way between our understanding of the universe and the Theory of Everything.
Dark Matter and Dark Energy
In his final lecture of the workshop, Prof Nath explored the missing mass problem in the universe, the methods we adopt to detect Dark Matter and Dark Energy, and the formation of the first stars.
The problem he approached very systematically was how a dust grain is important to initiate the formation of a star, and—a dust grain necessarily being a heavy element—the early universe had non of it. This posed a problem as to how the very first stars formed. He explained the Hydrogen and electron addition to create a hydrogen molecule which, being the heaviest thing present then, acted as a sufficiently large ‘dust grain.’
Prof Nath explored the inhomogeneity in the cosmos and how it was increasing and causing matter to clump, providing such wonderful examples and simulations as the Millenium Simulation created by the Max Planck Institute. He ended his lecture brushing the concept of how one would detect intergalactic trace elements and how the planned Murchinson Widefield Array of telescopes in the West Australian desert is expected to ‘keep astrophysicists busy for the next decade or so.’
Prof Uday Shankar’s first of two talks dealt with a broad introduction to Radio Astronomy, its usefulness and history and some technical aspects associated with it. In an hour sprinkled with informal communication and anecdotes of his own life as a student, Prof Shankar went on to explore how specific intensity of radio signals is dependent of spatial distribution of radio emission, its frequency, its wavelength, its polarisation studies and time period.
He related the times of Karl Jansky and Grote Reber and their discovery of radio astronomy as a science and building of the first radio telescope, respectively. He ended his introductory lecture listing the three major achievements of radio astronomy: the observations of the 21cm radiations of hydrogen; the detection of pulsars, quasars &c. and how it helped look back up to about 0.8 times the age of the universe; and, lastly, its discovery of Cosmic Microwave Background Radiations.
Bremsstrahlung, Black Holes and Binary systems in X-ray astronomy
The emission of X-rays of various types, by various phenomenon, the expulsion of X-rays owing to accretion discs in binary systems and the role of the distance of the Innermost Stable Circular Orbit [ISCO] in black holes of the prograde, non-spinning and anterograde types formed the basis of Dr Sreekumar’s first lecture.
An ex-NASA physicist with a doctorate from the University of New Hampshire and presently working for ISRO, Dr Sreekumar had tonnes of experience and knowledge to share. His lucid explanation of how one ought to read a mapped version of the universe, understand Active Galactic Nuclei and the Unification Model made the splendid one hour seem to pass with unimaginable pleasure.
Promising to speak of ISRO’s forthcoming missions tomorrow—the last day of the workshop—Dr Sreekumar spoke of Bera Rubin, SOHO’s discoveries and the mysteries of the Sun’s corona, which we are yet to answer.
Thus ended the second day of the Astrophysics workshop. I decided to keep my explanation handy and brief so as not to bore my readers who are not particularly fond of physics jargon. The details of the day was as I have said and I would be more than happy to share my experiences in more detail if anybody would fancy learning how two days with great minds is. It does sound like fun, does it not?