The core and inner layers of the Sun rotate about four times faster than its surface, which contradicts all conventional ideas about its structure, according to an article published in the journal Astronomy & Astrophysics.
“The most plausible explanation for this mystery is that the core of the Sun rotates faster than its outer layers thanks to the energy it accumulated 4.6 billion years ago, when the sun was just beginning to form. This is a big surprise for us, and we want to think that we have discovered the first real traces of what the Sun looked like when it was born,”says astrophysicist Roger Ulrich from the University of California at Los Angeles (USA).
The speed of rotation of stars around their axis is an important characteristic for astronomers, as it allows you to calculate the age of a star, determine its type, understand how often "starquakes" occur inside it and find out if it has satellites. As a rule, young stars rotate faster than old ones, than scientists use when searching for "twins" of the Sun and "newborn" celestial bodies.
Observations of the last 40-50 years, according to Ulrich, indicated that the interior of the Sun should rotate around its axis at the same speed as the outer layers, on the basis of which many other ideas about the behavior and structure of other stars were built. It was incredibly difficult to test these hypotheses, since the traces of the rotation of the luminary's interior, the so-called hydrodynamic gravitational waves, cannot be seen on its surface, because they do not reach there.
Ulrich and his colleagues were able to trace their movement through the interior of the sun, observing another type of waves, seismic vibrations that occur in the deep layers of the sun during "sunquakes". Scientists have been following them for several decades using probes SDO, SOHO and a number of other space observatories, but these oscillations do not store information about the structure of the core and the deepest layers of the interior of the star.
The authors of the article suggested that seismic waves can interact with their gravitational "cousins" if they move towards the core of the Sun and then return back. These interactions, in turn, should be reflected in how their structure changes over time.
Similar ideas, as noted by astrophysicists, had occurred among their colleagues before, but their verification was virtually impossible due to the fact that gravitational waves in the interior of the Sun are very slow - one of their oscillations can take from several days to several months. Therefore, scientists did not try to look for their traces in how faster seismic waves change.
The SOHO probe has continuously monitored the interior of the Sun for over 16 years, which allowed Ulrich and his team to begin searching for such bursts in archived data, analyzing them using supercomputers.
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This analysis revealed an extremely interesting thing that astronomers initially did not believe: it turned out that the frequency of gravitational waves in the core of the Sun did not coincide with that which was characteristic of its outer layers. As shown by the calculations of scientists, the core of the star should rotate about four times faster than its outer layers, and make one revolution around the axis in a week, and not in 28-30 days, like the surface of the Sun.
Why this happens is not yet clear, but Ulrich and his colleagues believe that the rotation of the outer layers of the Sun is slowed down by the solar wind, which is constantly ejected from its surface. In addition, their rotation can be slowed down by sunspots and other magnetic structures in the near-surface layers of the star.