First analysis of stellar winds from three sun-like stars

Astrospheres, analogous to the heliosphere that surrounds our solar system, are bubbles of plasma blown into interstellar space by stellar winds. These winds are responsible for numerous processes that affect planetary atmospheres. Studying the stellar winds from low-mass stars like the Sun helps us understand the evolution of stars and planets, including our own star and its system.


An international research team, including a CNRS researcher (see box), has for the first time detected X-ray emissions from the astrospheres of three solar-type stars, thus providing new constraints on the mass loss rates of these stars. This study, based on observations with the XMM-Newton space telescope, is published in Nature Astronomy in April 2024.

Primarily composed of protons and electrons, stellar winds also contain a small amount of heavier ions (e.g., oxygen, carbon), which emit X-rays when they capture electrons from interstellar neutrals.

Within our solar system, this so-called charge exchange emission is observed around the planets, comets, and in the heliosphere, and acts as a natural laboratory for studying the composition of the solar wind. However, observing it in astrospheres is challenging due to its low brightness. Moreover, the great distance of the stars complicates the separation of the astrosphere's signal from that of the star itself.

The researchers measured the spectral lines of oxygen ions with XMM-Newton to quantify the oxygen content and ultimately determine the total mass of the winds emitted by the stars.

In the future, high-resolution instruments, such as the X-IFU spectrometer of the European Athena mission, will facilitate the direct detection of stellar winds in X-rays, opening new perspectives for studying these phenomena.


Reference:
Kislyakova, K.G., Güdel, M., Koutroumpa, D. et al. X-ray detection of astrospheres around three main-sequence stars and their mass-loss rates. Nat Astron (2024)