American astrophysicists are going to study the atmosphere of distant planets on the fraction of oxygen in their gas shell.
Oxygen is the third most abundant chemical element in the Universe after hydrogen and helium.
It is an essential component of the clouds of gas and dust which forms new stars and planets.
The neutral atoms of oxygen in the spectra give intense lines, which are often used for calculations of the content of this element in different cosmic objects, methods of spectral analysis. Models of stars, giving the forecast of the number of oxygen corresponding to the true quantities of this element in stars, calculated according to the intensity of these lines, take into account the radiation field, the movement of hot gas stars and internal structure of stars (for example, the character of changes of temperature and pressure along the radius). However, as it turned out, a variety of assumptions taken for this calculation can lead to significant differences in predictions of oxygen analysis obtained on the basis of different models. If we talk about the giant stars, then the estimated oxygen content can vary among themselves in some cases up to 15 times.
In the new study, astronomers of the Harvard-Smithsonian astrophysical center Andrea Dupree, Eugene Avrett and Bob Kurucz make an attempt to solve this fundamental problem by using a computer code called PANDORA, created by Euratom for stellar atmospheres. In particular, in this model included the effects of the outer atmosphere of the giant stars, which are usually not considered in other models. Moreover, in this model, the level of excitation of oxygen atoms (and the intensity of corresponding lines) are not tied to the local temperature. This limitation, commonly used in early models to simplify the calculations, not adequately included in the calculation of more complex situations (e.g., hot air), the scientists write.
One of the applications of this new model is that it can help to clarify the amount of oxygen present in the circumstellar nebulae, which are formed exoplanets.
Work has appeared in the Astrophysical journal.
