The Orion Arm, or Orion–Cygnus Arm, is a minor spiral arm of the Milky Way galaxy. It is of interest because the Solar System (including the Earth) is inside it. The spiral arm is some 3,500 light-years (1,100 parsecs) across and approximately 10,000 light-years (3,100 parsecs) in length.
The Orion Arm is named after the Orion constellation, one of the most prominent constellations. It is seen in the Northern Hemisphere during winter and in the Southern Hemisphere during summer. Some of the brightest stars and most famous celestial objects are in the Orion Arm: Betelgeuse, Rigel, the stars of Orion's Belt and the Orion nebula. They are shown on the interactive map below.
The Orion Arm is between the Carina–Sagittarius Arm (toward the Galactic centre) and the Perseus Arm (toward the outside Universe). The Perseus Arm is one of the two major arms of the Milky Way. The Solar system is on the Orion spur, between the two longer adjacent arms Perseus and Carina-Sagittarius.
Inside the Orion Arm, the Solar System is close to the inner rim, in the Local Bubble. It is about halfway along the Orion Arm's length, about 8,000 parsecs (26,000 light-years) from the Galactic centre.
- See the "Spiral Arms" part of this NASA animation for details
- Also known as Local Arm, Orion Bridge, Local Spur and Orion Spur
- Harold Spencer Jones, T H. Huxley, Proceedings of the Royal Institution of Great Britain, Royal Institution of Great Britain, v. 38–39
- Earth's Milky Way neighborhood gets more respect, National Radio Astronomy Observatory, Dave Finley, 3 June 2013
- Vázquez, Ruben A. et al 2008. "Spiral structure in the outer galactic disk. I. The third galactic quadrant". The Astrophysical Journal. 672 (2): 930–939. arXiv:0709.3973. Bibcode:2008ApJ...672..930V. doi:10.1086/524003.