Orion Arm

We live in a long arm in space.

This arm is part of our big galaxy. It is called the Orion Arm. It gets its name from a group of stars.

Our home, the Earth, is inside this arm. It is near the edge.

The arm has many bright stars. It also has clouds of gas. These clouds help make new stars. It is a very busy place in space.

We live in a part of our galaxy called the Orion Arm.

It is also known as the Orion-Cygnus Arm. This arm is a part of the Milky Way. It holds our Solar System and the Earth.

The arm gets its name from the Orion constellation. This is a group of stars seen in winter. Many bright stars live here. You can see stars like Rigel and Betelgeuse. The Orion Nebula is also in this arm.

Scientists once thought this arm was a small piece. They called it a spur. A spur is a small part that sticks out. But new studies show it is much bigger. It may be a full arm itself. The arm is about 20,000 light-years long. It is about 3,000 light-years wide.

Our Sun sits in a space called the Local Bubble. This is a cavity in the gas of the arm. The arm sits between two other large arms. These are the Carina-Sagittarius Arm and the Perseus Arm. The Orion Arm is a very busy place for making stars.

The Orion Arm is a special part of the Milky Way galaxy.

It is also called the Orion-Cygnus Arm or the Local Arm. This structure holds our entire Solar System and the Earth. It is a major feature in our galactic neighborhood. Scientists often call it the fifth feature of the Milky Way. It sits between two other large arms. These are the Carina-Sagittarius Arm and the Perseus Arm.

This arm works through a process called a spiral density wave. This wave moves through the galaxy and pushes gas together. When gas is compressed, it helps new stars form. The Orion Arm contains many high-mass star-forming regions. These are places where big, bright stars are born. The arm also has a mix of gas and stars. Some stars are older than the gas clouds. There is even a small offset between where gas sits and where stars are.

For a long time, people had different ideas about this arm. Many scientists once thought it was just a small "spur." A spur is a minor structure that sticks out from a larger arm. However, new evidence changed how we see it. In 2013, researchers shared new findings about its size. They used data from the BeSSeL Survey to look closer. This study looked at the motion of masers in star-forming areas. These masers are special signals from space.

The arm is much larger than we used to think. It is about 20,000 light-years long. It is also about 3,000 light-years wide. The arm wraps around less than a quarter of the Milky Way. Our Sun is located near the inner rim of this arm. We live in a space called the Local Bubble. This is a relative cavity in the interstellar medium. The arm has a pitch angle of about 10.1 to 11.6 degrees.

You can find many famous objects in the Orion Arm. The name comes from the Orion constellation. This constellation is very bright in the winter sky. You can see stars like Betelgeuse and Rigel there. The arm also holds the famous Orion Nebula. There are many other Messier objects here too. These include the Pleiades and the Ring Nebula. You might even see the Butterfly Cluster. These objects help us map our place in the galaxy.

The Orion Arm is a major structure within the Milky Way galaxy.

It is also known as the Orion–Cygnus Arm or the Local Arm. This galactic feature encompasses our entire Solar System, including the Earth. Scientists often refer to it as the fifth feature of the Milky Way. It serves as our cosmic neighborhood within the larger spiral galaxy. Understanding this arm helps us map our specific location in space.

This arm is located between two other large galactic structures. It sits between the Carina–Sagittarius Arm and the Perseus Arm. The Carina–Sagittarius Arm projects toward the Galactic Center. The Perseus Arm forms the main outer-most arm of our galaxy. Our Solar System is positioned near the inner rim of the Orion Arm. We are located about halfway along the arm's total length. We also reside in a relative cavity called the Local Bubble. This bubble exists within the arm's interstellar medium.

The arm works through a process involving spiral density waves. These waves move through the galaxy and compress interstellar gas. This compression triggers the formation of new stars. The Orion Arm contains many high-mass star-forming regions, or HMSFRs. These regions are areas where large, bright stars are born. Researchers have observed that star formation lags behind gas compression. This happens because the density wave lasts longer than star formation timescales. These timescales are estimated between 10^7 and 10^8 years. This process creates a visible offset between gas and stars.

For a long time, astronomers held different views of this structure. They previously identified it as the Local Spur or Orion Spur. A spur is a minor structure between larger arms. However, evidence presented in 2013 changed this scientific view. The BeSSeL Survey, or Bar and Spiral Structure Legacy Survey, provided new data. They analyzed the parallax and proper motion of many interstellar masers. These masers are found in high-mass star-forming regions. The survey looked at more than 30 methanol and water masers. This research suggests the arm is more than just a minor spur.

Recent measurements show the Orion Arm is quite large. It has a length of approximately 20,000 light-years. The width of the arm is about 3,000 light-years. It wraps around less than a quarter of the Milky Way. The arm has a pitch angle between 10.1° and 11.6°. Scientists used the Gaia DR2 mission to map stellar density. They studied stars that are about 1 billion years old. These stars are more evolved than the gas in star-forming regions. This helped researchers compare gas distribution to stellar density.

The arm is named after the prominent Orion constellation. This constellation is very bright in the winter Northern Hemisphere. It is also visible in the summer Southern Hemisphere. Many famous celestial objects reside within this arm. You can find the bright stars Betelgeuse and Rigel here. The three stars of Orion's Belt are also part of it. The Orion Nebula is one of the most well-known objects. Many Messier objects are also located in this region. These include the Pleiades and the Ring Nebula.

Many diverse objects populate the Orion Arm's vast space. It contains the Butterfly Cluster, also known as M6. The Ptolemy Cluster, or M7, is another resident. You can find many open clusters like M23, M25, and M29. The Dumbbell Nebula, or M27, is located here as well. Other notable objects include the Beehive Cluster, M44. The Owl Nebula, M97, is also found in this arm. These objects help scientists understand the composition of the arm. They show how gas and stars are organized together. This complex system connects our local space to the wider galaxy.