Stellar wind

Stars blow a wind of gas.

This wind comes from the star. It moves out into space.

Some winds are very slow. They blow out much mass. Other winds move very fast. These fast winds blow big bubbles.

Our Sun has a wind too. It is called the solar wind. It comes from the star's hot top. It is made of tiny bits.

Big stars can lose much weight. They lose half their mass. This changes how they live.

Space is full of these winds. They are a wild thing to see.

Stars blow a wind of gas into space. This gas comes from the top of the star. We call this a stellar wind.

Different stars have different kinds of winds. Some stars are near the end of their lives. These stars blow slow winds. But these winds move a lot of mass. Other stars have very fast winds. These winds can blow big bubbles in space.

Big stars can lose much of their weight. Some stars lose half of their mass this way. This changes how the star lives and grows. Our Sun also has a wind. We call the Sun's wind the solar wind. It comes from the hot corona. The corona is the outer part of the star. The solar wind is made of tiny bits. These bits are called electrons and protons. They are very hot. This heat lets them escape the star's pull.

The wind from a star like our Sun does not change much. But it changes big stars a lot.

Stars do more than just shine in the night sky. They also blow a steady flow of gas into space. This flow comes from the upper atmosphere of a star. Scientists call this a stellar wind.

These winds are not always the same shape. They do not always blow out in a perfect circle. Some winds are very focused in specific directions. Other winds spread out more broadly. These winds help shape the space around a star. They can even create bright arcs called bow shocks.

How these winds work depends on the type of star. Some stars use radiation pressure to push the wind. This happens when light pushes on dust in the star's atmosphere. Other stars use light to push on heavy elements. This includes elements like carbon and nitrogen. These winds can move at very high speeds. For example, some winds move over 2,000 km/s.

Other winds are much slower. Some move at only 10 km/s. These slow winds often carry a lot of mass. They are common in stars nearing the end of their lives.

Different stars show us many ways to make a wind. Red giants and supergiants are examples of stars with slow winds. These stars are often in the asymptotic giant branch stage. Young stars called T Tauri stars have very strong winds. Massive stars like type O and type B stars are different too. They have winds that move very fast. These high-energy winds can blow large bubbles in space.

A planetary nebula like NGC 6565 shows a cloud of gas. This cloud was once part of a star. The strong stellar wind pushed it away.

Our own Sun is a G-type star. It has its own special wind called the solar wind. This wind comes from the hot, magnetized corona. The corona is the outer part of the Sun. The solar wind is made of tiny, high-energy bits. These bits are called electrons and protons. They have about 1 keV of energy. The high temperature of the corona helps them escape. This heat lets them break free from the Sun's gravity.

Stellar winds change how a star lives its life. For a star like our Sun, the wind is not a big change. But for massive O stars, the wind is huge. These stars can lose 50% of their mass through winds. This loss happens while they are on the main sequence. Losing this mass changes what happens to the star later. It can even decide if a star becomes a white dwarf. Some stars might explode as supernovae instead. The wind helps decide the star's final fate.

A stellar wind is a continuous flow of gas. This gas is ejected from the upper atmosphere of a star. These winds are important because they shape the space around a star. They do not always blow out in a perfect sphere. Some winds are less collimated, which means they are not focused in narrow beams. However, they are generally not perfectly symmetric.

The way a wind works depends on the star's specific properties. In some stars, the wind is driven by radiation pressure. This occurs when light pushes on dust that has condensed in the upper atmosphere. In other massive stars, the process is slightly different. Radiation pressure acts on the resonance absorption lines of heavy elements. This includes elements such as carbon and nitrogen. These mechanisms determine how much mass a star loses and how fast the wind moves.

Different types of stars produce very different kinds of winds. Post-main-sequence stars are nearing the end of their lives. This group includes red giants, supergiants, and asymptotic giant branch stars. These stars often eject massive amounts of mass. Their winds are relatively slow, moving at velocities of about 10 km/s. In contrast, young T Tauri stars often possess very powerful stellar winds.

Massive stars, such as type O and type B stars, show another pattern. These stars have lower mass loss rates compared to red giants. However, their winds move at extremely high velocities. These speeds can range from 1,000 to 2,000 km/s. These high-energy winds are strong enough to blow stellar wind bubbles in space.

Our own Sun is a G-type star, and its wind is unique. We call the Sun's wind the solar wind. It is driven by the Sun's hot, magnetized corona. The solar wind consists mostly of high-energy electrons and protons. These particles have an energy of about 1 keV. Because the corona is so hot, these particles can escape the star's gravity.

Stellar winds have a massive impact on how stars evolve. For lower-mass stars like our Sun, the wind does not strongly influence evolution. However, for massive O stars, the impact is significant. These stars can shed as much as 50% of their mass while on the main sequence. This loss of mass changes the star's later stages of life. Even intermediate-mass stars are affected by this process.

Mass loss can even change the final fate of a star. Some intermediate-mass stars will eventually become white dwarfs. They become white dwarfs instead of exploding as supernovae only because they lost enough mass through their winds. This shows that stellar winds are a key factor in a star's life cycle.

We can see the results of these winds in space. For example, the star LL Orionis creates a bow shock. This bright arc forms as its wind collides with material in the Orion Nebula.

Another example is the planetary nebula NGC 6565. In this nebula, a cloud of gas was ejected from a star due to strong stellar winds.