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  • 7:35 AM, Saturday, 23 Mar 2019

Department of Earth and Space Sciences
Anand Narayanan, Ph.D.
Associate Professor

  • Ph. D.  Astronomy & Astrophysics, Pennsylvania State University, 2008
  • M. S. Astronomy & Astrophysics, Pennsylvania State University, 2004
  • B. Tech. Electrical & Electronics, College of Engineering – Thiruvananthapuram, 2001

  • Assistant Professor, Department of Earth & Space Sciences, IIST (2010 - 2014)
  • Assistant Scientist, Department of Astronomy, University of Wisconsin-Madison (2008 – 2010)
  • Graduate Researcher, Department of Astronomy & Astrophysics, Pennsylvania State University (2002 – 2008)


                         For more details, visit my -   PERSONAL PAGE


This 3 credit course deals with topics in Galactic and extragalactic astronomy. It will be taught from an observational astronomy perspective.

There are no formal textbooks for this course. Readings will be posted from time to time on this site. Those and your lecture notes should be sufficient. But I urge you to read the relevant portions from the books listed below to gain a wider and deeper perspective on the various topics.


Course Grading Policy

  • Written examinations will follow the usual pattern of two quizzes and a final

  • Occasionally short articles or journal papers relevant to the topic will be posted on this site. A date for class discussion based on these reading will also be posted. 15 minutes of some class hours will be spent on discussion. 2% of the course grade is allotted for your participation in these discussions.

  • Assignments will carry 10% of the course grade

  • Scribe Notes: You are expected to take turns to act as scribes for each class. The scribe note for each class has to be put together as a formal lecture note with figures and tables included. A LaTeX template for this will be emailed to you. The notes are due on the third day after the lecture. Your notes will be uploaded on this page. The correctness, quality, and promptness of submission of these notes will amount for 8% of the course grade. 


1) Due Date: January 14 (Monday) by midnight

Model the continuum emission from stars of spectral type O to F.

In a single PDF file,  submit the (a) code (b) plots of specific intensity vs. wavelength or frequency or photon energy. I would prefer photon energy.

Based on that give answers to :

     (1) Stars of which spectral type(s) are capable of producing   H II regions ?

     (2) the Lyman continuum photon flux from O, B and A stars (in units of number of photons emitted per second)

Hints: Integration needs to be done only from soft-Xrays to NIR photon energies. In wavelength units, this range corresponds to 4 nm to 5 micron, approximate. The step size you choose during integration could play a significant role in the outcome of your result. I suggest pushing the step size in wavelength to 0.1 Angstrom while integrating, if your computer allows.

Effective stellar photospheric temperatures you need to consider are: 45000K (O Stars), 30000 K (O Stars), 15000K (B stars), 9000K (A stars), 6500 K (F stars), 5700 K (G stars). The curves should have specific intensity along the vertical axis in units of J/s/m^2/eV/sr and energy of photons in eV along the horizontal axis.

To compute luminosity from Planck function, you will need the radii of these stars. Assuming main sequence stars, adopt realistic values for the radii, for stars of different spectral type. This page has some information:

2) Due Date: January 22, 2019 (Tuesday) - no submission; only class discussion

Read the paper Kalberla & Kerp (2009), sent by email, and find answers for the following. You don't have to make any written submission. Read the paper and come prepared to answer these questions. 

(a) some details on the LAB survey (Leiden/Argentine/Bonn)

(b) What are CNMs and WNMs?

(c) Why is H I a more sensitive, a better tracer of Galactic dynamics compared to stars? 

(d) What is the definition of “scale height”? Does the scale height of H I in the Galaxy vary with Galactocentric distance? If so, how?

3) Due Date: January 28, 2019 (Monday) by midnight

Plot, in a Hammer-Aitoff map with Galactic coordinates, the location of the stars in the bright star catalogue of Reed et al. (2003, 2005). The stellar data will be emailed to you. You may use available standard routines that generate an Aitoff grid, or you can use the information given in the uploaded file "Aitoff-grid-equation" to generate your own grid. In a single PDF file,  submit the (a) code (b) aitoff plot. The location of the stars should be indicated by reasonably big filled circles. Don't make the data points too tiny to be seen.

4) Due Date: February 4, 2019 (Monday) by midnight

Generate the following plots for the distribution of Galactic globular clusters. The globular cluster catalogue can be found in Harris, W.E., 1996, AJ, 112, 1487.  You can also download it from

(1) Galactic latitude vs. distance from Sun plot
(2) Aitoff map in Galactic coordinates

Based on the maps, answer the following:
Q1) What can be inferred about the Sun’s location within the Galaxy?
Q2) Does it look like our Galaxy has a morphological centre? If so, where is that centre located?

As always, your submission should be a single PDF file with your name mentioned.

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