(ORDO NEWS) — Scientists from the University of Porto (Portugal) proved that red giants can experience sharp structural disturbances in the inner core.
These gaps affect the fluctuations in the brightness of stars, which is available for astronomical observations.
Red giants represent the last stage in the evolution of main sequence stars, whose cores are composed of helium, and hydrogen combustion occurs in the outer shell.
As soon as helium begins to melt in the core, the red condensation stage begins, which is typical for stars with an initial mass of 0.5-3 solar masses, and the luminosity and temperatures of red condensation stars lie in a small range of luminosity and temperature.
Hydrodynamic gravitational waves (G-modes) propagate in the cores of red-clump stars vibrations of liquid matter, which is affected by gravity.
When they interact with acoustic waves (P-modes), mixed modes of light oscillations arise, which can be characterized using Fourier analysis, which makes it possible to expand a complex function into harmonic oscillations with different frequencies.
It is known that abrupt structural changes (or breaks) in the interiors of stars can have a significant impact on the frequency of the modes, which astronomers call a glitch, or “glitch”. The scale and amplitude of such failures depend on the position and size of the gap.
In the new work, the researchers analyzed the light curves of 359 giant stars with masses less than 1.9 solar masses in the red clump phase, obtained by the Kepler space telescope.
It turned out that 6.7 percent of the stars exhibit significant deviations from the usual mixed modes of brightness oscillations, which indicates strong structural breaks in the core.
According to two main theories, disruptions exist throughout the evolution of a star, but they are very weak, or the discontinuities are smoothed out by some unknown physical process.
The results of the study do not support the first scenario, however, further research is needed to confirm the second.
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