Center for Space and Habitability | University of Bern | 2016 July 21
Normally computers speed up calculations. But with his new pen-and-paper formula Kevin Heng of the University of Bern gets his results thousands of times faster than using conventional computer codes. The astrophysicist calculates the abundances of molecules (known as atmospheric chemistry) in exoplanetary atmospheres. Ultimately, deciphering the abundances of molecules allows us to interpret if features in a spectrum are due to physics, geology or biology.
With their sophisticated instruments, astronomers today not only detect new exoplanets outside our solar system but are able to characterize the atmospheres of some of these distant worlds. To know what to anticipate and when to be surprised theorists calculate the expected abundances of molecules. Kevin Heng, director of the Center of Space and Habitability (CSH) at the University of Bern, is an expert in these calculations. “The sun – and other stars – have a very definite proportion of chemical elements like hydrogen, carbon, oxygen or nitrogen”, he explains: “And there is a lot of evidence that planets form from the essence of stars.” But whereas in stars the elements exist as atoms, in the lower temperatures of exoplanetary atmospheres they form different molecules according to temperature and pressure.
At low temperatures, for instance, the dominant carrier of carbon is methane (CH4), at high temperatures it is carbon monoxide (CO). The network of possible chemical reactions is well known but very large. Therefore, conventional calculations are complex and very time-consuming. “I found a way to do this much faster by solving 99% of the problem on paper, before one even touches a computer,” says Kevin Heng. “Normally, one solves what we call a system of coupled, non-linear equations. I managed to reduce the problem to solving a single polynomial equation. Effectively, I ‘uncoupled’ the system of equations on paper, instead of using a computer.” Solving this polynomial equation then takes a fraction of the original computer time. ...
Analytical Models of Exoplanetary Atmospheres. III. Gaseous C-H-O-N Chemistry with 9 Molecules - Kevin Heng, Shang-Min Tsai
- arXiv.org > astro-ph > arXiv:1603.05418 > 17 Mar 2016 (v1), 15 Jul 2016 (v2)