Stellar winds discovered for three sun-like stars for the first time  Urania

Astrophysicists have been able to measure the loss of stellar mass due to stellar winds.

An international research team has made the first direct detection Astronomical winds Three Sun-like stars were identified by recording X-ray emissions from their atmospheres, and the rate at which stars lose mass through their stellar winds was determined.

Astronomical planets, their stellar counterparts com. heliosfery surrounding us Solar SystemThey are extremely hot bubbles of plasma blown by stellar winds inside them A medium between the starsA space filled with gas and dust. Studying the stellar winds of low-mass stars similar to our Sun allows us to understand the evolution of stars and planets, and ultimately the history and future of our star and our solar system. Stellar winds drive several processes that evaporate planetary atmospheres into space, resulting in a loss of atmospheric mass.

Although planetary escape rates over an hour or even a year are small, they work over long geological periods. The losses are cumulative and could be the deciding factor between a planet becoming a habitable world or an airless rock. Although important for the evolution of stars and planets, the winds of Sun-like stars are extremely difficult to contain. They consist mainly of protons and electrons, but also contain small amounts of heavier, highly charged ions (such as oxygen and carbon). These ions are what pick up electrons from the neutral interstellar medium around the star and emit them X ray.

X-ray emission from astronomical atmospheres has been detected
An international team led by Kristina Kislyakova, a senior researcher at the Department of Astrophysics at the University of Vienna, has detected for the first time X-ray emission from astronomical atmospheres around three Sun-like stars, called Main sequenceThese are stars in the early stages of their lives, and thus such winds are recorded directly for the first time. This allowed them to determine the rate at which stars lose mass through their stellar winds.

These results are based on telescope observations XMM-NewtonLeave published In natural astronomy. Scientists observed the spectral signatures (called spectral lines) of the oxygen ions and were able to determine the amount of oxygen and, ultimately, the total mass of the stellar winds emitted by the stars. In the case of the three stars whose astronomical spheres are detected, they are named 70 Eve, Epsilon Eridani I 61 swanScientists estimated their mass loss rates at 66.5 +/- 11.1, 15.6 +/- 4.4, and 9.6 +/- 4.1 times the Sun's mass loss rate, respectively. This means that the winds coming from these stars are much stronger than the solar wind, which can be explained by the stronger magnetic activity of these stars.

In the solar system, solar wind charge exchange emissions from planets, comets and the heliosphere have been observed and provide a natural laboratory for studying the formation of the solar windexplained Kristina Kislyakova, lead author of the study. Observing this emission from distant stars is much more difficult due to the weak signal. Moreover, the distance to the stars makes it very difficult to separate the signal emitted by the astrosphere from the actual X-ray emission of the star itself, some of which is “scattered” in the telescope's field of view due to instrument effects. We have developed a new algorithm to separate stellar and astronomical contributions to the emission and detected charge exchange signals originating from the oxygen ions of the stellar wind and the surrounding neutral interstellar medium of three main sequence stars. This is the first time that X-ray charge exchange emission from the astronomical atmospheres of these stars has been detected. Our estimated mass loss rate can be used as a benchmark for stellar wind models and extend our limited observational evidence for solar-like stellar winds.

Co-author of the paper, Manuel Gödel, also from the University of Vienna, added: For three decades, efforts have been made around the world to confirm the existence of winds around Sun-like stars and measure their strength, but so far only indirect evidence based on their secondary effects on the star or its surroundings has indicated the existence of such winds. Wind. Our group has previously tried to detect radio emissions from wind, but was only able to determine the upper limits of wind strength, without detecting the wind itself. Our new X-ray results pave the way for finding these winds and even directly imaging them and studying their interactions with surrounding planets.

In the future, this method of direct detection of stellar winds with X-rays will become easier with future high-resolution instruments such as X-IFU spectrometer Athens European Mission. The higher spectral resolution of the X-IFU spectrometer will capture more precise structure and emission ratio of oxygen lines (as well as other faint lines) that are difficult to distinguish with CCD Thermal emission from stars or exchange of non-thermal charges from astronomical atmospheres – explained Dimitra Kotroumba, a researcher at the National Center for Scientific Research, and co-author of the study.

Agnieszka Novak

more information:

Source: University of Vienna

Pictured: An infrared image of the shock wave (red arc) created by the massive supergiant star Zeta Ophiuchus in an interstellar dust cloud. The weak winds of Sun-like main sequence stars are very difficult to observe. Source: NASA/JPL-Caltech; NASA and the Hubble Legacy Team (STScI/AURA); C.R. O'Dell, Vanderbilt University

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