An international research team led by the University of Vienna has made a major breakthrough. In a study recently published in Nature Astronomy, they describe how they conducted the first direct measurements of stellar wind in three Sun-like star systems.
a study recently published in Nature Astronomy, they describe how they conducted the first direct measurements of stellar wind in three Sun-like star systems
The study of the stellar winds of low-mass stars similar to the Sun allows us to understand stellar and planetary evolution, and ultimately the history and future of our own star and solar system.
Stellar winds drive many processes that evaporate planetary atmospheres into space and therefore lead to atmospheric mass loss.
Although escape rates of planets over an hour or even a year are tiny, they operate over long geological periods.
The losses accumulate and can be a decisive factor for a planet evolving into a habitable world or an airless rock.
Despite their importance for the evolution of both stars and planets, winds of Sun-like stars are notoriously difficult to constrain.
X-ray emission from astropheres detected
An international research team led by Kristina Kislyakova, Senior Scientist at the Department of Astrophysics of the University of Vienna, has detected for the first time the X-ray emission from the astrospheres around three sun-like stars, so called main sequence stars which are stars in the prime of their life, and has thus recorded such winds for the first time directly, allowing them to place constraints on the mass loss rate of the stars via their stellar winds
What is a stellar wind in astronomy?
Stellar winds are fast-flowing streams of particles that are emitted from a star. Whilst stars may appear to be stable and static, they are in fact extremely hot, active and dynamic
What is the study of stars in astronomy?
Stellar astronomy studies the life cycle and structure of stars, both as individuals and as populations. By tracking the commonalities and differences that make stars what they are, we understand the appearance and contents of the visible universe. Stars are born out of cold dense clouds of gas and dust.
What is a stellar wind from our own sun called?
This flow of particles, called the “solar wind,” has an enormous impact on our lives. It protects us from stray cosmic rays coming from elsewhere in the galaxy—but the effects of storms on the sun’s surface can also affect our telecommunications networks
How does an astronomer measure stellar distances?
Astronomers use an effect called parallax to measure distances to nearby stars. Parallax is the apparent displacement of an object because of a change in the observer’s point of view.
What are the 4 types of astronomy?
We can divide astronomy into 4 sub-fields:
- ASTROPHYSICS: Applying the laws of physics in space.
- ASTROMETRY: Mapping celestial bodies.
- ASTROGEOLOGY: Examining rocks, terrain, and material in space.
- ASTROBIOLOGY: Searching for life outside Earth
How old is astronomy?
The first documented records of systematic astronomical observations date back to the Assyro-Babylonians around 1000 BCE. From this cradle of civilisation in Mesopotamia – in the southern part of present-day Iraq – astronomers had built up knowledge of the celestial bodies and recorded their periodic motions
Does astronomy require math?
In astronomy we use algebra, calculus, statistics and probability, but also trigonometry and logarithms to calculate things like movement, distances and even the chemical characteristics of distant stars and galaxies.
While stellar winds mainly comprise protons, electrons, and alpha particles, they also contain trace amounts of heavy ions and atomic nuclei, such as carbon, nitrogen, oxygen, silicon, and even iron. Despite their importance to stellar and planetary evolution, the winds of Sun-like stars are notoriously difficult to constrain. However, these heavier ions are known to capture electrons from neutral hydrogen that permeates the ISM, resulting in X-ray emissions. Using data from the XXM-Newton mission, Kislyakova and her team detected these emissions from other stars.
These were 70 Ophiuchi, Epsilon Eridani, and 61 Cygni, three main sequence Sun-like stars located 16.6, 10.475, and 11.4 light-years from Earth (respectively). Whereas 70 Ophiuchi and 61 Cygni are binary systems of two K-type (orange dwarf) stars, Epsilon Eridani is a single K-type star. By observing the spectral lines of oxygen ions, they could directly quantify the total mass of stellar wind emitted by all three stars. For the three stars surveyed, they estimated the mass loss rates to be 66.5±11.1, 15.6±4.4, and 9.6±4.1 times the solar mass loss rate, respectively.
In short, this means that the winds from these stars are much stronger than our Sun’s, which could result from the stronger magnetic activity of these stars. As Kislyakova related in a University of Vienna
In the solar system, solar wind charge exchange emission has been observed from planets, comets, and the heliosphere and provides a natural laboratory to study the solar wind’s composition. Observing this emission from distant stars is much more tricky due to the faintness of the signal. In addition to that, the distance to the stars makes it very difficult to disentangle the signal emitted by the astrosphere from the actual X-ray emission of the star itself, part of which is “spread” over the field-of-view of the telescope due to instrumental effects.”
Astrospheres, stellar analogues of the heliosphere that surrounds our solar system, are very hot plasma bubbles blown by stellar winds into the interstellar medium, a space filled with gas and dust
What can stellar winds tell us about planetary evolution?
Astrospheres, stellar analogues of the heliosphere that surrounds our Solar System, are very hot plasma bubbles blown by stellar winds into the interstellar medium, a space filled with gas and dust.
The study of the stellar winds of low-mass stars similar to the Sun allows us to understand stellar and planetary evolutionand, ultimately, the history and future of our own Sun and Solar System
Providing a benchmark for observing Sun-like stars
“In the Solar System, solar wind charge exchange emission has been observed from planets, comets, and the heliosphere and provides a natural laboratory to study the solar wind’s composition,” explained Kristina Kislyakova, lead author of the study.
What are the stellar winds of massive stars?
This extremely high luminosity has an interesting consequence: the light is so strong that it pushes away the outer layers of the star. In this way, a stellar wind is formed. The star is surrounded by this stellar-wind material which is steadily flowing away from the star, with speeds of up to 3000 km/s.
Where does stellar wind come from?
A “stellar wind” is the continuous, supersonic outflow of matter from the surface layers of a star. Our sun has a solar wind, driven by the gas-pressure expansion of the hot (T > 106 K) solar corona
Do all stars have stellar winds?
All stars, including those more massive than the Sun and those less massive, are believed to have stellar winds at some level
Which type of star has the strongest stellar winds?
These include red giants and supergiants, and asymptotic giant branch stars. These winds are understood to be driven by radiation pressure on dust condensing in the upper atmosphere of the stars. Young T Tauri stars often have very powerful stellar winds
Why is it called Stellar?
Stellar is Latin for ‘composed of stars’ or ‘characteristic of stars’. The actual word for star in Latin is Stella. Synonyms of Stellar are astral, star, starry. A star is defined as a “hot, gaslike, bright body in space, such as the Sun” and has its origin in the Greek word astro
What is the difference between solar winds and stellar winds?
Solar winds are gentle in motion, but can disrupt power on Earth. meanwhile Stellar Winds are more gentle and difficult to be detected from Earth because these stars are so distant when compared to the Sun. So collision won’t happen against these winds due to their gentleness in motions and their distances in between
Does the Sun have stellar wind?
As the Sun rotates (once every 27 days), it winds up its magnetic field lines above its polar regions into a large rotating spiral, creating a constant stream of “wind.” Such emissions, or streamers, are thought to come from large bright patches called “coronal holes” in the Sun’s corona, as seen in the image above.
Why do red giants have strong stellar winds?
Red giant stars tend to be even more unstable than blue giant stars, because they are so distended that gravity has a relatively feeble hold on their outer atmospheres. Moreover, their enormous luminosity pushes the envelope outward. As a result, every red giant star is losing mass in stellar winds.
Perhaps the place to begin is the realization that almost all stars evidently have “astrospheres”, all too transparent to be seen but undoubtedly as complex as our own heliosphere. The stellar wind is the creator of the astrosphere, just as the solar wind sweeps out the cavity in interstellar space that we call the heliosphere. Thus the origin of the heliosphere and the astrosphere traces back to the hydrodynamics of the million degree solar and stellar coronas. The solar corona appears to be created by the dissipation of mechanical and magnetic energy in the tenuous gas above the dense photosphere. It is that dissipation, evidently in the form of the microflaring in the magnetically “quiet” regions of the Sun, that creates the heliosphere. The staggering complexity of the convective and magnetic machinations on all scales down into the unresolved microstructure of the solar activity gives some idea of the mystery of the stellar corona and astrosphere. Indeed, the mystery does not stop with the microflaring, for we are in the dark as to the origin of the fibril magnetic fields that seem to drive the system from below the visible surface. With the variety of stellar types and circumstances that may be presumed to create stellar winds and astrospheres, the inquiry into the heliosphere and the extrapolation to other stars is bewildering.
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