Astronomers at Universidade of Tecnologia of Chalmers, at The discovery comes from detailed observations of the star R Doradus, located about 180 light-years from Terra. The study, published in the journal Astronomy & Astrophysics, indicates that other internal processes in the star act as the main responsible for the ejection of material.
The research used the SPHERE instrument, installed on Very Large Telescope of Observatório Europeu of Sul, on Chile. Scientists analyzed polarized light reflected by dust grains near the stellar surface.
- The detected grains consist mainly of silicates and alumina.
- Its average size is around 0.1 micrometer.
- Simulations have shown that these grains capture too little starlight to overcome gravity.
Even considering extreme scenarios, such as total condensation of available atoms into dust, the radiative force remains insufficient.
Observations with advanced telescopes
The team combined data from SPHERE with previous images taken by the Atacama Large Millimeter/submillimeter Array (ALMA). Essas observations revealed structures in the atmosphere of R Doradus, a star on the asymptotic giant branch with a mass similar to that of Sol.
The researchers tested radiative transfer models to simulate interactions between light and matter. The results confirmed that small grains scatter light, but do not accelerate the gas significantly.
Theo Khouri, leader of the study, highlighted that the team hoped to confirm the classic model, but the data showed the opposite. Ele considered the result exciting for science.
Iron-rich grains, which absorb more radiation, heat quickly and sublime before contributing to wind.
Featured Alternative Mechanisms
With dust ruled out as the main driver, astronomers turned their attention to the star’s internal processes. R Doradus presents regular pulses, with cycles of 175 and 332 days, which generate shock waves capable of ejecting gas.
Convection also plays an important role.
- Giant bubbles of hot plasma rise to the surface.
- They cool and descend, creating turbulence.
- This movement lifts material into regions where dust can later form.
Wouter Vlemmings, co-author of the study, stated that alternatives such as convective bubbles and intense episodes of dust formation deserve exploration. Esses processes best explain the release of the observed winds.
Implications for stellar evolution
R Doradus serves as a prototype for stars like Sol in advanced phases. Gigantes red colors enrich the interstellar medium with heavy elements, such as carbon, nitrogen and oxygen, essential for the formation of planets and life.
The discovery changes understanding about mass loss in these stars. Ventos stellar cells carry material that forms new generations of planetary systems.
Future observations need to track variations throughout the pulsation cycles. Isso will help identify when and how the winds pick up strength.
Details of the observed star
R Doradus is located in the constellation of Dorado and has a large angular diameter, facilitating detailed studies.
- Distance: approximately 180 light years.
- Mass loss rate: moderate, around 10^{-7} solar masses per year.
- Composition: rich in oxygen, typical of low to intermediate mass evolved stars.
The polarimetric data revealed a bright arc of scattered light around the stellar disk.
Next steps in research
The team plans new observational campaigns to monitor different phases of pulsational cycles. Isso will allow testing the role of convection and pulses in the initial acceleration of winds.
Theoretical models need to incorporate these combined mechanisms. The research integrates knowledge from astronomy, physics and chemistry to refine simulations.
