#Red #giant #stars #measure #Universe
The Large Magellanic Cloud full of bright red giant stars./ CTIO/NOIRLab/NSF/AURA/SMASH/D. Nidever (Montana State University)
A team of astronomers led by scientist Richard I. Anderson, from the École Polytechnique Fédérale de Lausanne (EPFL), has found a new method to measure cosmic distances accurately, using the phase of red giant of the stars.
This phase, expected to occur on our Sun in about 5 billion years, is characterized by the expansion of a star’s outer layers as its core collapses. The phenomenon not only signals destruction for the planets of the inner solar system, including Earth, but also affects any exoplanets orbiting similar stars in the universe.
Measure with edges
According to research published in The Astrophysical Journal Lettersthe “songs” or acoustic oscillations of red giants offer a new perspective on how to use the method of Red Giant Branch Tip (TRGB). This represents a new tool to address the problem known as the “Hubble tension.”
The TRGB is a critical point in the Hertzsprung-Russell diagram, which classifies stars according to their luminosity and temperature. At this point, the cores of the red giant stars have collapsed enough to initiate helium fusion, reversing their lighting process. This turns red giants into what astronomers call a “standard candle,” allowing the brightness of these stars to be compared at different distances and therefore measuring these cosmic distances accurately.
Hubble voltage
This method adds a new rung to the “cosmic distance ladder,” a set of techniques used by astronomers to measure vast distances in the sky. universe. From stellar parallax to analyzing the redshifts of distant galaxies, each technique represents a rung on this metaphorical ladder, contributing to our understanding of the expansion of the universe and the value Hubble constant.
However, the discrepancy between different measurement methods has generated the “Hubble tension”, a problem that raises questions about our understanding of the universe. The discovery could add a crucial rung to this ladder, using the oscillations of red giants to differentiate their age and therefore fine-tune their use as standard candles.
The study of these stars in the Large Magellanic Cloud, using data from the Optical Gravitational Lensing Experiment (OGLE) and the Gaia mission, revealed that TRGB stars periodically vary in brightness due to sound waves traveling through them, similar to how earthquakes travel through the Earth. This variation allows us to determine the age of the red giants and improve the measurement of cosmic distances.
