It seems that one cannot look inside the star. However, a team of scientists from the Max Planck Institute for Solar System Research was able for the first time to determine the deep internal structure of two stars based on their vibrations.
Our Sun, like most stars, experiences pulsations that propagate along the inside like sound waves. The frequencies of these waves are imprinted on starlight and can be later noted by terrestrial astronomers. In the same way as seismologists study the planetary structure by earthquakes, astronomers determine the stellar properties by pulsations.
The two studied stars belong to the system 16 Swan (A and B) and resemble the Sun. They are 70 light years away from us, so they seem relatively bright and suitable for analysis.
To create a model of the star's interior, stellar evolutionary models need to be changed until one of them correlates with the observed specific spectrum. But pulsations in theoretical models often differ from stellar ones. So, some part of stellar physics is still not disclosed. Therefore, the researchers decided to use the reverse method. They deduced the local properties of the stellar region from the observed frequencies. This method relies less on theoretical assumptions, but requires accurate measurement of the data. It is also complex from a mathematical point of view.
Using this method, scientists have sunk into the stars by 500,000 km and found that the speed of sound in the central regions is greater than the models show. In the case of Cygnus 16, these differences are explained by errors in the determination of stellar parameters, but in 16 Cygnus A, no obvious reasons were found.
Perhaps, while certain physical phenomena are not available to us, which should be taken into account when drawing up models. This is just the first structural analysis. Scientists plan to test another 10–20 additional stars using the Kepler telescope information. More data will be available with future TESS and PLATO missions.
