Superbubble

Huge bubbles live in space.

Big stars make them. These stars have strong winds. The winds blow gas away. This makes a big hole.

Stars also explode. These big blasts help the bubble grow. The bubbles hold very hot gas.

As they grow, they sweep up dust. This dust forms a shell around the bubble.

Our own sun lives near one. It is called the Local Bubble. It is a very big part of space.

Huge bubbles live in deep space. We call these superbubbles. They are hundreds of light years wide.

Big stars make these bubbles. These stars live in groups called OB associations. These stars have very strong winds. These winds blow gas away from the stars. This makes a small bubble. In a group, these small bubbles merge. They form one giant superbubble.

When these big stars die, they explode. These are called supernovae. These explosions send out huge blast waves. The blasts push the bubble even more. The inside of a superbubble is very hot. It holds gas that is 106 K.

As the bubble grows, it sweeps up gas and dust. This material forms a thick shell around the hole. We can see these shells in many ways. Some show up as X-rays. Others show up as light we can see.

Our sun lives near an old superbubble. It is called the Local Bubble. Some bubbles are so big they blow through a galaxy. We sometimes call these chimneys.

Space is filled with huge, empty areas called superbubbles. These cavities are hundreds of light years across. They are not truly empty, though. They are filled with very hot gas atoms. This gas is much less dense than the space around it. These giant structures are carved out of the interstellar medium. This is the material that sits between the stars.

How do these bubbles form? It starts with groups of massive stars. These groups are called OB associations. These stars have very strong stellar winds. These winds push gas away to make small bubbles. Inside an OB association, these small bubbles merge together. This merging creates one giant superbubble. The winds of newly born stars also strip away dust. This helps keep the inside of the bubble clear.

When these massive stars reach the end of their lives, they explode. These explosions are called supernovae. A supernova can release a huge amount of energy. The blast waves from these explosions move very fast. They can reach speeds of several hundred kilometers per second. Most of these explosions happen inside the existing cavity. The energy travels through the hot interior as sound waves. Both winds and explosions help the superbubble expand.

Scientists use different light to see these structures. They first saw shells using hydrogen light at twenty-one centimeters. Younger bubbles often show up in X-ray emissions. We can also see them through visible light. Older objects might be called supershells. These happen when many superbubbles combine into one. Some bubbles are so large they act like chimneys. They blow through a whole galactic disk.

We can find examples of these in our own sky. Our Solar System sits near an old superbubble. This is known as the Local Bubble. We can trace its edges by looking at distant stars. Other famous examples include the W4 superbubble. You can also find the Henize 70 superbubble. It is located in the Large Magellanic Cloud. There is also the Orion-Eridanus Superbubble. These structures show us how stars change their galaxies.

A superbubble is a massive cavity in space. These structures can be hundreds of light years across. They are not completely empty spaces. Instead, they are populated with very hot gas atoms. This gas has a temperature of about one million Kelvin. The gas inside is much less dense than the surrounding interstellar medium. The interstellar medium is the material found between stars. Superbubbles are carved out of this medium by powerful forces. These forces include stellar winds and multiple supernovae.

The formation of a superbubble begins with massive stars. These stars have masses between eight and roughly one hundred solar masses. They are often found in groups called OB associations. These groups include O-type and early B-type stars. Massive O stars produce very strong stellar winds. These winds release a kinetic energy of 10^51 ergs over a star's life. This amount of energy is equivalent to a supernova explosion. These winds create individual stellar wind bubbles that are dozens of light years across. Inside an OB association, these bubbles merge. This merging process creates a single giant superbubble.

Supernovae also play a major role in powering these structures. When massive stars die, they explode as supernovae. These explosions drive blast waves into the surrounding space. These waves can reach expansion velocities of several hundred kilometers per second. Most of these explosions happen inside the cavity already formed by stellar winds. Because they occur in the hot interior, they may not form a visible supernova remnant. Instead, they expend their energy as sound waves. Both the winds and the explosions work together to expand the superbubble.

As the superbubble expands, it affects the surrounding gas. The interstellar gas swept up by the bubble generally cools down. This cooling forms a dense shell around the cavity. Scientists can observe these shells using different types of light. They were first observed via line emission from hydrogen at twenty-one centimeters. This discovery helped researchers create the theory of superbubble formation. We can also see them through X-ray emission from their hot interiors. Other researchers use optical line emission from ionized shells. Infrared continuum emission can show dust that was swept up into the shells.

There are different stages and types of these large structures. Younger superbubbles are typically observed through X-ray and visible light. As they grow older and larger, they may change. Some very large objects are called supershells. A supershell can result from multiple superbubbles combining together. Some superbubbles can become large enough to act like chimneys. These structures can blow through an entire galactic disk. They release energy into the surrounding galactic halo. They may even release energy into the intergalactic medium.

We can find evidence of these structures in our own neighborhood. Our Solar System lies near the center of an old superbubble. Astronomers call this the Local Bubble. We can trace its boundaries by looking at exterior stars. There is a sudden rise in dust extinction at distances greater than a few hundred light years. This change helps mark the edge of the bubble. Other notable examples exist throughout the universe. The W4 superbubble is a candidate for a chimney structure. The Henize 70 superbubble is located in the Large Magellanic Cloud.

Many different superbubbles help us understand how galaxies work. Examples include the Ophiuchus Superbubble and the Scutum Supershell. The Orion-Eridanus Superbubble and the Perseus-Taurus Shell are also known. These structures show how energy moves through space. They demonstrate how the life and death of stars shape the interstellar medium. By studying these cavities, we see the connection between individual stars and the larger galactic environment.