Milky Way Arms ssc2008-10

Observed structure of the Milky Way's spiral arms[1]

The Orion Arm is a minor spiral arm of the Milky Way galaxy some 69 across and approximately 69 in length.[2] The Solar System and therefore 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.

Our Local 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 in fact a branch of the Perseus Arm, or possibly an independent arm segment itself.[3]

Within the Orion Arm, our Solar System and Earth are located close to the inner rim in the Local Bubble, about halfway along the Orion Arm's length, approximately 69 from the Galactic Center.

Messier objects


The shape of the Orion Spur[4]

The Orion arm contains a number of Messier objects:

Interactive maps

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See also


  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. Vázquez, Ruben A.; May, Jorge; Carraro, Giovanni; Bronfman, Leonardo; Moitinho, André; Baume, Gustavo (January 2008). "Spiral Structure in the Outer Galactic Disk. I. The Third Galactic Quadrant". The Astrophysical Journal 672 (2): 930–939. DOI:10.1086/524003.

External links

Template:Earth's location

Template:Milky Way

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