The Solar Oxygen Crisis

Astrophysicist writes "The Astrophysical Journal this week published an article about the abundance of oxygen in the Sun. Oxygen is the third most abundant atom in the universe, behind hydrogen and helium. Most of the hydrogen and helium was formed in the Big Bang, which means that oxygen is the element most frequently produced by nuclear fusion reactions in the interior of the stars. The solar abundance of oxygen, which is key in astrophysics because of its use as a calibration reference for other objects, was thought to be well established since the 80s. However, recent evidence indicates that it has been overestimated by almost a factor of two. A revision of the solar oxygen abundance would have a cascading effect on other important elements, such as carbon, nitrogen and neon, whose abundance is only known relative to that of oxygen. In addition to the impact on the chemical composition of many stars, models of solar interior may require some reworking in order to be consistent with the new data."

Comments

How the solar oxygen abundance is derived

[Agent Orange]

This is not a new issue in astrophysics, and has been floating since 2004. There are two basic ways to measure the abundances. One is by looking at hte oscillations in the sun, and using those to probe the solar interior. This is called "helioseismology", since it is very similar to the way seismologists figure out the structure and composition of hte earth, by observing seismic waves.

The other way is to take a spectrum of the sun (which is really just the solar photosphere -- the outer layers, or "atmosphere"). To interpret the spectra, one needs a model, which is used to derive the abundance (how much oxygen there is).

Now...until recently the models used for deriving abundances were simple 1-dimensional models, which made some assumptions (such as "local thermodynamic equilibrium") and include some fudge factors to account for the fact that you're solving a 3-d problem in 1-d.

The oxygen problem arises when you use accurate, 3-D models, which don't make the LTE assumption mentioned above -- called non-local thermodynamic equilibrium (NLTE). When one compares the abundances from the 3d NLTE models with what is expected from the helioseismology predictions, the discrepancy arises.

Others have posted the link to the full journal article on the pre-print server (here). The introduction of this paper is a pretty good summary of the problem, albeit intended for a scientific audience.

Re:WE'RE ALL GOING TO DIE!

[Thagg]

There is a long tradition of this in physics. My favorite was "The Ultraviolet Catastrophe", which forecast that all energy would be increasing in frequency.

The point of this kind of tounge-in-cheek hyperbole is to get people thinking about problems in a more creative, out-of-the-box way, and lead them toward solutions. The Ultraviolet Catastrophe led directly to Planck's quantum hypothesis -- which I don't think he even took as a serious solution at the time. But, it took that kind of wacky idea to get people over the hump of classical theory.

I think that the Solar Oxygen Crisis people are trying to do something similar.

Thad Beier