Astronomers have created a model linking the rate at which some planets are losing their atmosphere to various external factors. This algorithm allows predicting how the thickness of the atmosphere of celestial bodies with a certain mass will change under the influence of external factors. The work was published in the journal Astronomy & Astrophysics.
Observations from NASA's Kepler telescope have revealed a huge variety of exoplanets - planets outside the solar system. The masses and radii of most of them are between those for Earth and Neptune (they are usually divided into super-Earths and mini-Neptune). The large number of planets of these types found is due to the fact that, unlike planets the size of the Earth, they are relatively easy to detect.
Exoplanets have long attracted scientists as models for studying the evolution of celestial bodies. The data obtained from the study of planets outside the solar system will help to learn more about the evolution of the Earth. The processes associated with the creation of the atmosphere play an important role in understanding the mechanisms of their formation. In addition, the atmosphere of exoplanets is much easier to study than their surface, about which it is often impossible to obtain any data.
One of the most indicative processes in the formation of the atmosphere is the escape of atmospheric particles into outer space. As a result of this phenomenon, the gas shell of the planet disappears under the influence of various factors: the attraction of a satellite or another planet, increased temperature, solar wind, and others. This process can be most clearly traced for planets with a hydrogen atmosphere, since it is most susceptible to the influence of external factors due to its lightness.
An international team, which included an employee of the Siberian Federal University (SFU), created a model based on data on more than 7,000 exoplanets. All of them had masses from 1 to 39 Earth masses, and hydrogen predominated in their atmosphere. For each planet, scientists have determined the intensity of heating of the upper atmosphere under the action of X-ray and ultraviolet radiation from the star, the density of atmospheric gas and the rate of its outflow. Then the researchers developed an automated algorithm that was able to independently calculate the maximum dissociation (the decay of molecules into atoms), ionization (obtaining charged ions from neutral atoms) of the atmosphere, the rate of loss of the planet's mass and the effective absorption radius of radiation (the distance from the center of a celestial body over which it absorbs star light). These are the quantitieswhich determine the nature of the evolution of the atmosphere. All of them were presented in the form of a large data array, distributed according to the main parameters of the planet: mass, radius and radiation intensity of the star. Then the scientists used interpolation - a mathematical algorithm that allows you to extend the found dependence to any required intermediate value within the boundaries of the model.
“Our grid and interpolation routine allows us to quickly get information that would otherwise take days or weeks to compute. This makes it possible to use the results of calculations of the rates of mass loss in the study of the evolution of the planet's atmosphere over a long period. You can also avoid the need to use previously used approximate formulas, which can underestimate or overestimate a number of important factors,”says one of the authors of the work, Professor of the Siberian Federal University Nikolai Erkaev.
