Our galaxy has a flat part.
It is made of stars and dust. Most stars live here. It is where our Sun stays. It is a very big place. Can you look at the stars?
Our galaxy has a flat part.
It is made of stars, gas, and dust. Most stars live in this part. Our Sun stays here too.
This part is called a thin disk. It is younger than other parts. It grew from gas that gathered.
Some stars are very old. Some stars are new. They all live in the disk.
Long ago, a small galaxy may have hit us. This shook up the stars. Then, the gas settled back down.
It is a very busy place in space.
A galaxy can have a flat shape. This part is called a thin disk.
The thin disk is made of stars, gas, and dust. It holds most of the matter in a galaxy. In our Milky Way, it has about 85% of the stars in the galactic plane. It even has 95% of all the stars in the disk. Our Sun lives in this part. It sits about 8,000 light-years from the center.
This disk is younger than the thick disk. The thick disk has very old stars. The thin disk grew from gas that gathered later. Because of this, thin disk stars have more heavy elements. Scientists think the thin disk formed 8.8 billion years ago.
How did it form? A small galaxy may have hit ours. This hit shook up the stars. This made the thick disk. Then, the gas settled back down. This gas made the thin disk again. The thin disk has many groups of stars. These groups have different ages.
A galaxy can have a flat shape. This part is called a thin disk.
The thin disk is a main part of spiral galaxies. It is also part of S0-type galaxies. This disk is made of stars, gas, and dust. It holds most of the matter in a galaxy. Most of this matter is not in the center. The thin disk is a very important structure.
Think about how a disk is shaped. It has a height and a length. The thin disk has a scale height. This is the height on the vertical axis. It is perpendicular to the disk. It also has a scale length. This is the length on the horizontal axis. This length goes in the direction of the radius. The Sun lives in our thin disk. It is 8,000 light-years from the center.
Scientists have studied how this disk formed. They use a science called nucleocosmochronology. This helps them find the age of the disk. Experts like Eduardo F. del Peloso have studied this. They looked at stars to find the age. They think the thin disk formed a long time ago. It likely formed 8.8 billion years ago. This number has a small range of 1.7 billion years.
There are many facts about these stars. The thin disk has 85% of the stars in the galactic plane. It has 95% of all the stars in the disk. These stars are different from thick disk stars. The thick disk has older stars. Those stars have fewer heavy elements. Thin disk stars are made from gas accretion. This means gas gathered to make them. These stars have more heavy elements.
How did the thin disk get its shape? A small satellite galaxy may have hit ours. This collision shook up the stars. That shaking created the thick disk. After the hit, the gas settled down. It settled into the galactic plane. This gas then reformed the thin disk. The thin disk has many groups of stars. These groups have different ages.
The thin disk is a vital structural part of certain types of galaxies. It is found in spiral galaxies and S0-type galaxies. This disk is made of stars, gas, and dust. It represents the main area of matter density outside of the galactic center. The center is often called the galactic bulge.
The thin disk is where most of the active material in a galaxy resides. It serves as a primary building block for the galaxy's overall shape.
To understand the disk, we look at its dimensions. Scientists measure it using scale height and scale length. The scale height is the measurement along the vertical axis. This axis is perpendicular to the flat disk. The scale length is measured along the horizontal axis. This axis follows the direction of the radius.
In our own Milky Way galaxy, the Sun is located within this thin disk. The Sun sits about 8,000 light-years away from the galactic center.
The thin disk is distinct from the thick disk of a galaxy. These two parts are separated by the age and composition of their stars. The thick disk is made of an older population of stars. These stars were created during an earlier stage of galaxy formation. Because they are older, they contain fewer heavy elements. In contrast, the thin disk is considered considerably younger than the thick disk.
Stars in the thin disk form through a process called gas accretion. This means that gas gathers together to create new stars. Because these stars form at later stages, they are more metal-rich. This means they have a higher amount of heavy elements. The thin disk contains stars with a very wide range of ages. Scientists can even divide these stars into sub-populations based on how old they are.
Astronomers use a science called nucleocosmochronology to study these structures. This method helps them estimate how old the Galactic thin disk is. Researchers such as Eduardo F. del Peloso and his team have studied this. Their work involves looking at specific elements to find the age. Based on this science, the thin disk formed about 8.8 billion years ago. There is a margin of error of about 1.7 billion years for this estimate.
The thin disk holds a massive proportion of a galaxy's stars. In the Milky Way, it contains about 85% of the stars in the Galactic plane. Furthermore, it accounts for 95% of the total stars found in the disk. This shows how much matter is concentrated in this flat layer.
These numbers highlight why the thin disk is the primary component of the galactic disk.
Scientists believe a major event may have shaped these layers. The Milky Way may have collided with a smaller satellite galaxy. This collision would have caused a massive disturbance. The impact likely shook up the existing stars. This shaking process is thought to have created the thick disk.
After the collision, the gas behaved differently than the stars. The gas settled back into the galactic plane. This settled gas then reformed the thin disk we see today.
Where will your curiosity go next?
🖼️ Images & Media (1)
More to explore
✨ What else?
Related topics you might enjoy
🪜 Step back
Simpler topics to build understanding
What is Nepedia?
A free, ad-free encyclopedia for children. Every article is written at five reading levels, so the same page works for a five-year-old and a fifteen-year-old — use the level switcher above to see this one change. No account needed to read.