See the syllabus for more details about the different options for the paper/project. No matter the type of activity chosen (review, calculation, data analysis, paper critique), the topic should be relevant to the overall scope of the course, but going beyond the material given in the lecture notes.
The term project contributes 30% to the final grade, and that is broken down as follows:
- 10: Paper (original work) goes beyond what was presented in class; contains no major math or logic errors; results presented clearly.
- 5: Paper: (background) conveys motivation for studying this topic; shows evidence of wider reading than just the textbooks.
- 5: Paper: (format) adequate length; proper grammar and spelling; appropriately serious tone; consistent formats for citations, figures, equations.
- 10: Presentation: clarity; clarity; clarity!
CHOOSING A TOPIC:
A list of example topics is given below, but you're encouraged to find something that interests you. Note that Wednesday, March 7, 2018 is the deadline for submitting your idea for a topic (email or paper please; not just a hallway conversation). The topic can certainly evolve after that point, but it's good to have an initial idea developed midway through the course.
THE PAPER:
- This component is due on TBD DATE. Please email the document to me (preferrably in PDF, but MSWord or other formats are okay). If you can, please also turn in a paper version in class, but that's not required; it's just for my own ease of grading.
- If you scroll down a bit on my tips and tricks web page, you'll see some links to resources for scientific writing. Of course, another excellent way to learn is to read lots of scientific papers and internalize the styles and practices you see.
- EXAMPLE TERM PAPERS:
- With some hesitation, I give you a link to my own quarter-century old term paper from a solar physics course I took at the University of Delaware. (Apologies for the low-res scan, but no fully electronic version exists - the figures were hand-pasted into place!) Please don't use this as too literal a guide, however. For one thing, in that class the paper was only supposed to be a literature survey, so it's not exactly analogous to the one in this course.
- On the opposite extreme (i.e., a computation-heavy paper with nearly no literature survey) is this short paper on polytropic models (original source link here). It is actually an MIT professor's solution to an assigned problem set, but nonetheless it is of the right order of magnitude in length and "depth" as the computational work appropriate for a project like this.
- Of course, googling "How to write an astronomy paper" will bring up lots of useful hints and tips, also....
THE PRESENTATION:
- In the last week of classes, I anticipate setting aside 2 to 3 sessions for in-class presentations. Once we know how much time per student will be available, make sure to set aside roughly a quarter of it for questions and informal back-and-forth. Feel free to divide up the "talking time" how you like, but if roughly half is devoted to background and motivation for your topic, and half is devoted to presenting your own work, you're probably in good shape.
- You can decide on whether your presentation will be high-tech (Powerpoint or Keynote) or low-tech (whiteboard only). The goal is something roughly in between a short talk at the AAS and an informal "whiteboard session" (i.e., what you've been warned about for Comps II). I'm glad that our classroom has whiteboard space to the left of the projector screen, so we can switch back and forth between the two easily.
- On my tips and tricks page, I've assembled links to several good guides to giving scientific talks.
EXAMPLE TOPICS:
The following topics are just suggestions. Please feel free to choose something else. Other ideas are spread throughout the books and lecture notes linked on the course web page.
- When discussing equations of state in class, I didn't say much about the gradual transitions between the various cases (ideal gas, radiation pressure dominated gas, non-relativistic electron degeneracy, ultra-relativistic electron degeneracy). However, one can write down fully general equations based on what was discussed in the lecture notes. Explore what the equation of state looks like at an arbitrary point in the temperature/density diagram.
- People often write the virial theorem with extra terms that we didn't discuss in class (e.g., magnetic energy, time-variable moment of inertia). What can we learn about stellar physics when these terms are included? George Collins, author of our primary textbook, also wrote a short monograph on The Virial Theorem that discussed lots of this.
- Do we really understand the elemental abundance distribution (X, Y, Z) of the present-day Sun? Maybe not! Solar interior models constructed with the most recent photospheric values of Z seem to be in disagreement with helioseismology. Is there an "Oxygen Crisis?"
- When discussing the mixing-length theory of convection, I mentioned a complicated cubic polynomial that describes the full (inefficient and non-adiabatic) problem. Track down a good derivation of this cubic equation (say, in Cox & Giuli's Stellar Structure) and show how one can turn the "efficiency knob" to obtain the temperature gradient in both limits of convective stability and instability.
- Rotating polytropes: In lectures we discussed the Roche model (infinite concentration of mass at the center) and briefly mentioned the opposite case (a rotating incompressible droplet). Can you formulate the equations for something "in between?" How does a star's equator-to-pole radius ratio at critical/breakup rotation depend on the internal equation of state of a star?
- Solar evolution models say that, about 4 billion years ago, the Sun's luminosity was only about 0.7 times its current value. If that was true, the Earth should have been a frozen ice-ball. The geological record, however, says it was warm and wet. Carl Sagan pointed this out in the 1970s, but are we any closer now to a solution to the Faint Young Sun Problem?
- Stellar pulsations: One can use our tried-and-true constant density model (the n=0 polytrope) as a background state and solve for the eigenfrequencies and eigenfunctions of p-mode oscillations as "simple" polynomials.
- Supernova light curves: In class, I briefly mentioned David Arnett's 1982 analytic model of SN light curve energetics. Digesting and implementing this model -- and exploring what happens when its parameters are varied -- could make for an interesting learning experience.
- Supernova dynamics: In class, we cover some discrete stages of kinematic expansion (constant velocity, Sedov-Taylor, etc). Some additional exploration of the transitions between these phases would be interesting. Also, a more detailed derivation of one of the final stages (the cooling-dominated snowplow phase) was left out of the lecture notes. Carrying out that derivation, together with an investigation of a proposed stage earlier than Sedov-Taylor (r ~ t^0.6), could contribute to a good project paper, too.
- There are plenty of interesting things that can be done with MESA, a public stellar interiors/evolution code. See some recent papers here, here, and here that describe its capabilities.
- In the past, students have sometimes written papers that focus on a single type of interesting star... e.g.,
- Classical novae are white dwarfs in close binary systems that undergo explosive nucleosynthesis from thin layers on their surfaces.
- Some pulsating stars have amplitudes and periods that vary slowly in time -- sometimes (in the case of RR Lyrae stars undergoing the "Blazkho effect") in a chaotic manner!
- CEMP (carbon enhanced metal poor) stars may be candidates for being "relic" Population III stars from the early universe.
- T Tauri stars are young, low-mass stars that are still accreting matter from gaseous disks. A small fraction of them (FU Orionis objects) undergo huge flare-like outbursts.
- Do Thorne-Zytkow objects (red supergiants with neutron-star cores) really exist?
- Hot subdwarfs (sdO/sdB) are the cores of horizontal branch stars (i.e., core helium burning stars) that lost their (thin) H envelopes in a "quiet" way - i.e., without going back up the red giant branch.
- What's up with Przybylski's Star exhibiting plutonium lines in its spectrum?
- Can we tell neutron stars apart from strange stars made up of exotic baryons?
- Googling the phrase "weird types of stars" may return a few interesting items, too.