Astronomy lecture-workshop — Day 3

I still do not know why somebody said ‘All good things end,’ but they did and they did.

Today was the last day of the Astronomy lecture-workshop hosted by Yuvaraja’s College, Mysore and convened by the Science Academies of India. If you have not read them already, you can see what happened on the first day, here; and go through my report of the events on the second day, here.

On the last day we had just two lectures signalling the end of eleven remarkable hours that stood for everything in this workshop. The two lectures were by Prof Uday Shankar of the Raman Research Institute and Dr Sreekumar from ISRO.

Questions galore

Prof Uday Shankar opened our eyes in one way—and nobody can deny that: the fact that we stop (or have already stopped, in some rare cases,) questioning the trivial things around us. In fact he made this clear by firing questions at us regularly and insisting that we must find the answers ourselves.

So let me take a little deviation here to state his questions and that I am still finding out the answers to some of them, so I will probably write an article or two explaining the stuff once I find out. In the meantime, if you get to it first, feel free to share below!

  • Why are only few frequencies of radiations allowed past the ionosphere?
  • How many different types of molecules have been discovered in Radio Astronomy?
  • What are some famous types of molecules that are also subjects of study in other disciplines of astronomy?
  • Which type, among translational, rotational etc. of these is actually dominant in Radio Astronomy?
  • How are parsecs and lightyears related?
  • What are the frequencies of Short Wave, Medium Wave and Frequency Modulated radio signals?

On I (?,?,?,P,t)

Prof Uday Shankar began his talk with a quick recap of yesterday’s lecture and continued with a detailed explanation of how a radio telescope works and how it uses Fourier transformation of wavefronts. As he explained the parabolic structure of the Radio telescope dish and the path of incident waves on it, I (and perhaps a few others) found it almost enlightening to understand a real-life example of a mathematical model, the real-life example of the use of what were, up to this point, merely theories although they were no less interesting.

It was one of those surges of enthusiasm to deal with science that every aspiring scientist feels—and needs—now and then.

Yesterday we had discussed a formula that went I (?,?,?,P,t) and today Prof Uday Shankar spent quite some time patiently explaining how we arrive at a determination of each of them and how they matter in the equation.

Having explained the continuums of thermal and synchrotron radiations and the spectral lines of spectral line emission, he moved on to explain the resolution properties of radio telescopes.

An interesting question he mentioned that he usually asked at interviews went thus: at what distance can you, as an observer, differentiate between a two-wheeler and a four-wheeler?

The point was that the human eye can resolve up to 1” (arc sec) and the maximum distance we could do so was about 3.6 kilometers if we took the resolution of either one (two-wheelers) or two (four-wheelers) headlights. This was analogous to a radio telescope resolving a bright speck in the sky either as a system/apparent alignment of two stars or just one.

And to meet the resolving power of the human eye, a radio telescope had to be a mighty 27 km in circumference! Clearly, this was impossible and he explained—as a solution to this—Ryle and Hewish’s Aperture Synthesis process using Young’s method to obtain a number of interferences that could later be added up to obtain a final image. He also parenthetically mentioned the Gauribidanur Radioheliograph near Bangalore and the Giant Metrewave Radio Telescope near Pune.

As he finished his talk, he gave us little details of the Raman Research Institute’s Visiting Student Programme. My friend, Subramanya Hegde, who shares my enthusiasm for physics (and is definitely better established at it, anyway!) has compiled this interesting list of such similar visiting student/summer/scholarship programmes for anybody who is interested.

Challenges in outer space

Like we do not have enough challenges down here on Earth, we have bigger ones in outer space (one major hinderance being the fact that one must wear a seven-layer suit for EVA even in low-earth orbit!)

The challenges space poses for X-ray astronomers and the troubles in detecting a neutral particle like the photon and how these brilliant astrophysicists overcame it was the topic of the last lecture of the workshop by Dr Sreekumar.

He spoke of how high vacuum outgassing, unchecked space radiations and trapped charged particles in the Van Allen Belts are problematic to X-ray astronomers. After a fleeting mention of the South Atlantic Anomaly over Brazil, Dr Sreekumar explained the payload of ISRO’s upcoming mission, Astrosat.

He then explained how it becomes difficult to catch X-rays owing to their sparse distribution and unpredictable occurrences (as opposed to Radio Waves) in the universe. Then he explored the Scanning Sky Monitor [SSM] and a simple photon detector and how it works.

He then ventured to examine what properties of the photon actually matter to us (energy, arrival direction, polarisation state, and arrival time.) He also briefly showed us the Geant 4, Garfield/ANSKS/Maxwell and Charge Transport simulations; and a very basic Bolometer.

He ended his talk with a look at Point Spread Function, and a comparison between a normal pin-hole camera and the process of Coded Mask Imaging. The last bit was a quick slideshow of perhaps previously unseen pictures of the various stages of developments and the various payloads of ISRO’s Astrosat on which project Dr Sreekumar is working presently.

And it all ends

The last part of the workshop saw Dr Sreekumar telling us aspiring scientists all about how one could get into ISRO, the qualifications they look for, the kind of posts available, when best to apply, how best to approach their interviews and how he believes the scales are tipping towards pursuers of the pure sciences.

A brief valedictory function later, the lot of us had lunch, interacted with each other, exchanged a few ideas and left the workshop, three days having been spent better than we could ever have hoped for!

And that is how it all ended.