Honors project

Honors project#

Examples of past honor’s projects#

The honor’s project consist in installing on your machine MESA, and use it to investigate something we will barely touch upon in class.

The list below contains some examples, if you are interested in doing an honor’s project for this class, please come talk to me to define a scope that best fits your interests and the content of this class.

Main sequence burning in massive population III stars#

Nuclear burning in massive stars occurs through the CNO cycle, which uses metals (Carbon, Nitrogen, and Oxygen) as catalysts to stick together 4 protons, turn two of them into neutrons, and produce helium. However, what happens when C, N, and O are not available?

One physical situation where we think this may have happened is for Population III stars, the first stars formed from pristine material from the Big Bang: those only had H and He (and maybe some trace Li and Be), no C, N, or O was available in the gas cloud they formed from. N.B.: we have not seen these stars, but clearly at some point they must have existed! The only way to study how they evolved for now is through numerical simulations.

In this project you will compute with the stellar evolution code MESA the evolution of two 30M~⊙~ non-rotating, non-magnetic, single stars, one at solar metallicity Z~⊙~ and one with Z=0, until the end of hydrogen core burning, compare their evolution in terms of their potentially observable surface properties and in terms of their interior structure, and interpret the differences.

Instructions#

  • Follow the MESA documentation to install the code

  • Follow the tutorial to run MESA: this will be your Z~⊙~ 15M~⊙~ star!

  • By reading the documentation, figure out what to change to make this a 30M~⊙~ star and run it until "terminal age main sequence" (end of H core burning).

  • By reading the documentation, figure out which options to change to set Z=0 (hint: there should be more than one!), and run a second, Z=0, 30M~⊙~ star (otherwise identical to the tutorial model)

  • Plot as many things as you wish to understand the physical differences between the two models and write up a short text (<4 pages including figures) with your findings. Focus on the physical processes in the stellar interior and why they may differ, and put them in the context of the course material.

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