About

Who. Frederic Petrignani, a student doing a capstone project in computational chemistry and astronomy, on a laptop, in the evenings and weekends.

What. Large flat carbon molecules called PAHs (polycyclic aromatic hydrocarbons) glow in the infrared everywhere in space. Telescopes such as JWST record their light in great detail. To read that light we need to know, for each molecule, exactly which colours of infrared it absorbs and emits. For small molecules we can measure that in a laboratory. For the big ones we cannot, so we have to compute it. The project builds and tests a pipeline that tries to compute those spectra accurately enough to be useful, and, just as importantly, says clearly when it cannot.

Rules of this blog. Everything here follows the same rules as the project itself:

• Every number comes from a script that anyone can run, and each post names the commit it was taken from.
• I say what was measured, not what I hope will happen.
• Plans change by dated notes, not by quietly rewriting old text. Old posts stay as they were; corrections are added, dated, at the bottom.

Where the work lives. The plans, scripts and results are in the public repository thebreadishard/udacity-capstone-plan.

The atlas

The catalogue behind these posts is the Spectrum Atlas: the molecules, their status on the ladder, the harmonic frequencies and the provenance of every number, updated from the project repository at each build.