Orion Arm

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

The Orion Arm, or Orion–Cygnus Arm, is a minor spiral arm of the Milky Way galaxy.[2] 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.[3]

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.[4]

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.

The shape of the Orion Spur[5]

Interactive map[change | change source]

Rosette NebulaSeagull NebulaCone NebulaCalifornia NebulaHeart NebulaOrion NebulaSoul NebulaNorth America NebulaCocoon NebulaGamma Cygni NebulaVeil NebulaTrifid NebulaCrescent NebulaLagoon NebulaOmega NebulaEagle NebulaCat's Paw NebulaEta Carinae NebulaCrab NebulaMessier 37Messier 36Messier 38Messier 50Messier 46Messier 67Messier 34Messier 48Messier 41Messier 47Messier 44Messier 45Messier 37Messier 52Messier 93Messier 7Messier 6Messier 25Messier 23Messier 21Messier 18Messier 26Messier 11Messier 35NGC 2362IC 2395NGC 3114NGC 3532IC 1396IC 2602NGC 6087NGC 6025NGC 3766NGC 4665IC 2581IC 2944NGC 4755NGC 3293NGC 6067NGC 6193NGC 6231NGC 6383Tr 14Tr 16Messier 103Messier 29HPerChi PerCol 228O VelPerseus ArmOrion ArmSagittarius ArmStar clusterNebula
The nearest nebulae and star clusters (clickable map)

References[change | change source]

  1. See the "Spiral Arms" part of this NASA animation for details
  2. Also known as Local Arm, Orion Bridge, Local Spur and Orion Spur
  3. Harold Spencer Jones, T H. Huxley, Proceedings of the Royal Institution of Great Britain, Royal Institution of Great Britain, v. 38–39
  4. Earth's Milky Way neighborhood gets more respect, National Radio Astronomy Observatory, Dave Finley, 3 June 2013
  5. 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. doi:10.1086/524003.