Red supergiant stars 'dance' because they have too much gas

[Admin]

A new study has revealed why red supergiant stars appear to dance around in the space.

Red supergiant stars 'dance' because they have too much gas : Read more

 

[rod]

The space.com report stated, "Astronomers can typically determine the near-exact location of a star by identifying its photo-center, or the point at the center of the light it emits, which usually lines up perfectly with its barycenter, or gravitational center. In most stars, photo-centers occupy fixed positions. But in red supergiants, this point appears to wobble across the star, moving slightly from side to side over time. That motion makes it hard to pinpoint the stars' barycenters, which provide stars' exact cosmic addresses and don't move around like the jiggling photo-centers do."

I read the paper and the wobble is very small angular size

Reference paper, Probing red supergiant dynamics through photo-center displacements measured by Gaia⋆, https://www.aanda.org/articles/aa/full_html/2022/05/aa43568-22/aa43568-22.html, 06-May-2022. “Abstract Context. Red supergiant (RSGs) are cool massive stars in a late phase of their evolution when the stellar envelope becomes fully convective. They are the brightest stars in the universe at infrared light and can be detected in galaxies far beyond the Local Group, allowing for accurate determination of chemical composition of galaxies. The study of their physical properties is extremely important for various phenomena including the final fate of massive stars as type II supernovae and gravitational wave progenitors. Aims. We explore the well-studied nearby young stellar cluster χ Per, which contains a relatively large population of RSG stars. Using Gaia EDR3 data, we find the distance of the cluster (d = 2.260 ± 0.020 kpc) from blue main sequence stars and compare with RSG parallax measurements analysing the parallax uncertainties of both groups..."

My observation. Consider that 1" angular size at 2.26 kpc = 2.2600E+03 AU. The abstract indicates the RSG in the Double Cluster are pinned down to 0.033 to 0.130 AU variation. 1 mas angular size = 2.2600E+00 AU diameter so seeing 0.033 to 0.130 AU at 2.26 kpc is some viewing here .

The paper summary and conclusions, “5. Summary and conclusions We used Gaia EDR3 measurements of parallaxes and proper motions of blue main sequence stars and determined the distance of the χ Per cluster. The mean value of the parallaxes of is 0.442 +/- 0.004 mas corresponding to a distance of d = 2.260 ± 0.020 kpc. We then selected a subset of RSG stars, with proper motions in the same domain as the blue stars, and find pronounced evidence that the measured Gaia uncertainty of parallaxes is higher than those of the blue star sample. With the aim of explaining the high uncertainties, we used the snapshots from a grid of RHD simulations of RSG stars to compute intensity maps in the Gaia G photometric system. The synthetic maps show extremely irregular surfaces due to convection-related dynamics. The largest structures evolve on timescales of months/years, while the small ones on timescales of weeks/month. Consequentially, the position of the photo-center is expected to change as a function of time during Gaia measurements. We calculated the standard deviation (σP) of the photo-center excursion for each simulation and found that σP varies between 0.033 and 0.130 AU (≈1 to ≈5% of the corresponding stellar radius) depending on the simulation…”

My note, using my telescopes if I can see clearly down to 1.5 arcsecond angular size, is good. These folks use better tools than I have to pin down RSG positions