天文学者、これまでで最も詳細な映像で恒星表面の気泡を追跡(Astronomers track bubbles on star’s surface in most detailed video yet)

2024-09-11 チャルマース工科大学

＜関連情報＞

• https://news.cision.com/chalmers/r/astronomers-track-bubbles-on-star-s-surface-in-most-detailed-video-yet,c4035922
• https://www.nature.com/articles/s41586-024-07836-9

進化した巨大恒星の表面における1ヶ月の対流タイムスケール One month convection timescale on the surface of a giant evolved star

Wouter Vlemmings,Theo Khouri,Behzad Bojnordi Arbab,Elvire De Beck & Matthias Maercker
Nature  Published:11 September 2024
DOI:https://doi.org/10.1038/s41586-024-07836-9

Abstract

The transport of energy through convection is important during many stages of stellar evolution^1,2, and is best studied in our Sun³ or giant evolved stars⁴. Features that are attributed to convection are found on the surface of massive red supergiant stars^5,6,7,8. Also for lower-mass evolved stars, indications of convection are found^{9,10,11,12,13}, but convective timescales and sizes remain poorly constrained. Models indicate that convective motions are crucial to produce strong winds that return the products of stellar nucleosynthesis into the interstellar medium¹⁴. Here we report a series of reconstructed interferometric images of the surface of the evolved giant star R Doradus. The images reveal a stellar disk with prominent small-scale features that provide the structure and motions of convection on the stellar surface. We find that the dominant structure size of the features on the stellar disk is 0.72 ± 0.05 astronomical units. We measure the velocity of the surface motions to vary between −18 and +20 km s⁻¹, which means that the convective timescale is approximately one month. This indicates a possible difference between the convection properties of low-mass and high-mass evolved stars.