Orion Arm

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For the stars which form the arm of the Orion asterism, see Orion (constellation). For the online project, see Orion's Arm.
Observed structure of the Milky Way's spiral arms[1]

The Orion Arm is a minor spiral arm of the Milky Way some 3,500 light-years (1,100 parsecs) across and approximately 10,000 light-years (3,100 parsecs) in length.[2] The Solar System, including the Earth, lies within the Orion Arm. It is also referred to by its full name, the Orion–Cygnus Arm, as well as Local Arm, Orion Bridge, Local Spur and Orion Spur.

The Orion Arm is named for the Orion constellation, which is one of the most prominent constellations of Northern Hemisphere winter (Southern Hemisphere summer). Some of the brightest stars and most famous celestial objects of this constellation (Betelgeuse, Rigel, the stars of Orion's Belt, the Orion Nebula) are located within the Orion Arm, as shown on the interactive map below.

The Orion Arm is located between the Carina–Sagittarius Arm (toward the Galactic Center) and the Perseus Arm (toward the outside Universe), the latter one of the two major arms of the Milky Way. Long thought to be a minor structure, a "spur" between the two longer adjacent arms Perseus and Carina-Sagittarius, evidence was presented in mid 2013 that it might be a branch of the Perseus Arm, or possibly an independent arm segment itself.[3]

Within the Orion Arm, the Solar System, including Earth, is located close to the inner rim in the Local Bubble, about halfway along the Orion Arm's length, approximately 8,000 parsecs (26,000 light-years) from the Galactic Center.

Messier objects

File:OrionSpur.png
The shape of the Orion Spur[4]

The Orion Arm contains a number of Messier objects:

Interactive maps

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See also

References

  1. ↑ See the "Spiral Arms" part of this NASA animation for details
  2. ↑ Harold Spencer Jones, T. H. Huxley, Proceedings of the Royal Institution of Great Britain, Royal Institution of Great Britain, v. 38–39
  3. ↑ Earth's Milky Way Neighborhood Gets More Respect, National Radio Astronomy Observatory, Dave Finley, 3 June 2013
  4. ↑ Lua error in package.lua at line 80: module 'strict' not found.

External links

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