CCNY PHYS 45400 Sp 2025

Homework 4

Make an HR diagram

1. Choose some selection criteria and make an HR diagram.
   1. Use Simbad to get some data about stars. https://simbad.cds.unistra.fr/simbad/sim-fsam. Choose a selection criteria that will contain a reasonable number of stars, preferably with various spectral types. i.e. don't just pick all the red stars, then your HR diagram will be biased.
   2. Create a python (jupyter notebook) that will process that data. Here's the example we did in class: https://colab.research.google.com/drive/1tukDjv3GlNoeZxzIBNhLs344dWtAGd2t?usp=sharing
   3. Figure out how to convert the various stellar data into values that are appropriate for the two axes of an HR diagram.
   4. Make an HR diagram of your stars.
   5. Explain how the HR diagram illustrates something about the population of stars.

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For all

• Include your sources and a table of the raw data you used. (This ideally would be a link to your data file online somewhere, like a github repository or google drive link. Make sure sharing is set properly so that with a single click, it can be viewed.)
• Make sure all plots are formatted nicely and have labeled axes.

Due Date: Wednesday April 2, start of class. (via blackboard brightspace.)

Prepare your work in a typed (no handwritten math or drawn diagrams), document (pdf) with plots and any citations for any references you used, and links to any extensive code you wrote that was used.

If you used any AI to help with code, please cite that. Under no circumstances do I want to read any AI generated text though.