When studying a star like Betelgeuse, it is indeed possible to detect changes in its composition as different layers of elements are created within it. However, it's important to note that the direct observation of the internal layers of a star is challenging because we can only observe the light emitted by the star's surface.
Nevertheless, by analyzing the star's spectrum, which is the distribution of its light across different wavelengths, astronomers can indirectly infer the composition of a star, including the presence of different elements. Each element in a star's atmosphere leaves a unique signature or "fingerprint" in its spectrum, which can be identified through spectroscopic analysis.
By examining the absorption lines in the spectrum of a star like Betelgeuse, astronomers can identify the elements present in its outer layers. These absorption lines occur when elements in the star's atmosphere absorb specific wavelengths of light, creating dark lines at those wavelengths in the spectrum.
As a star evolves, nuclear reactions occur in its core, causing the synthesis of heavier elements from lighter ones. These newly synthesized elements can eventually be mixed to the surface through various processes such as convection or stellar winds. Therefore, changes in the surface composition of a star like Betelgeuse can provide indirect information about the nuclear reactions and element production happening within it.
Additionally, changes in the observed spectral lines can also indicate variations in the stellar atmosphere, temperature, and other physical properties. Monitoring these changes over time can help astronomers understand the processes occurring inside the star and its evolutionary stage.
It's worth mentioning that Betelgeuse, being a red supergiant star, is of particular interest because it is expected to undergo a supernova explosion in the future. Studying its composition and changes in its spectra can provide valuable insights into the final stages of massive stellar evolution and the processes leading to supernova explosions.