A team of astronomers has found new evidence that red giant stars suffer from “gaps” (sharp structural differences) in their inner cores, RT reports. Red giants are dying stars, in advanced stages of stellar evolution, that have depleted the hydrogen in their cores.
In the study, published in Nature Communications, by a team of astronomers led by the Institute for Astrophysics and Space Sciences (IA) in Lisbon, Portugal, scientists collected the internal structure of more than 350 stars by studying the oscillating patterns. seen in their roofs.
The researchers used data from NASA’s Kepler space telescope and a technique known as “seismology” to delve into the cores of ancient stars, much like seismologists use to explore the interior of our planet.
Red giants are large, bright stars about 0.3 to 8 times the mass of the Sun that have reached an advanced stage of stellar evolution. Stars like the Sun release energy by converting hydrogen into helium through nuclear fusion, but the supply of hydrogen in the inner core is limited.
And when that begins to wear off – and the outward pressure from the merger recedes – they collapse under their own gravity. At this point, the star’s temperature rises until it reaches the point at which hydrogen fusion can begin, but this time in a shell around the star’s inner core.
The energy released in this process causes the star’s outer layers to expand dramatically, to hundreds of times their previous size. As a result, the star’s surface cools and turns red, giving these objects their name.
Since red giants are used in many scientific studies, such as astronomical distance probes, to help measure galactic density and study the chemical evolution of stars, it is important to be able to model their internal structure correctly.
Although the interior of the red giant cannot be seen directly, it is possible to deduce its internal structure by measuring the oscillations that appear on the surface of stars as a result of the frequencies and paths of sound waves passing through stellar bodies.
Stars have many different oscillation modes that are sensitive to different parts of their interiors, and seismologists can use these patterns to probe different aspects of stellar structure.
The astronomer at the Institute of Astrophysics and Space Sciences, Dr. Daisy Cunha. “These waves reveal the conditions of the medium in which they propagate, that is, the physical properties of the stellar interior.” .
In the study, Kuna and his colleagues investigated 359 red giants below a certain mass threshold, measuring different properties, including different oscillation frequencies, for each star.
The principal astronomer, Dr.
He added that this allows “for the first time to conduct an accurate survey of the physical processes that occur in this region. By analyzing these differences, we can obtain not only the general parameters of the star, but also information about the exact structure from these structures.”
The analysis revealed that approximately 7% of the stars studied suffer from structural discontinuities – so-called ‘rifts’ within their inner cores.
According to scientists, two hypotheses have been put forward to explain how this defect works. The first suggests that they were present during the evolution of stars, but they are generally too faint to be classified as true provinces. The team says that this scenario is not supported by the results of their study.
The second hypothesis proposes that this defect is “dissolved” by an unknown physical process that subsequently leads to changes in the structure of the star’s inner core.
However, more accurate data will be needed before scientists can focus on this idea. As astronomer Diego Pausini of the Institute of Astrophysics and Space Sciences explains: “This study shows the limitations of our models and gives us the opportunity to find a way to improve them.”