ALMA reveal giant gas bubbles on star R Doradus

The discovery was presented in the renowned journal "Nature." Until now, the Sun was the only object on whose surface movements of matter had been observed. The technique of interferometry allowed for viewing other stars' surfaces, but not with the precision provided by the latest research.

R Doradus, a red giant with a diameter 350 times greater than the Sun and located just 590 light years from Earth, became an excellent candidate for detailed observation. The ALMA radio telescope network located on the Chajnantor plateau in Chile was used for this purpose.

Scientists conducted observations in July and August 2023. These revealed the existence of gigantic bubbles of hot gas with sizes 75 times larger than our Sun. The bubbles appeared on the star's surface and then sank back into its interior. Understanding this mechanism, known as "convection," is crucial not only for the theory of star and planet formation but also for the future of our own Sun.

Convective processes on the surface of R Doradus can provide valuable information about the evolution of stars, especially since they are difficult to observe on other stars.

Convection creates the beautiful granular structure seen on the surface of our Sun, but it is hard to see on other stars. With ALMA, we have now been able to not only directly see convective granules — with a size 75 times the size of our Sun! — but also measure how fast they move for the first time, Theo Khouri from Chalmers University of Technology in Sweden.

The movements of the granules on the surface of R Doradus turned out to occur in a one-month cycle. This is a faster rate than previously thought, given the current knowledge of convection on the Sun. It remains unclear what causes this discrepancy; it may be related to the aging of stars.