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 Nebula Seagull Nebula Cone Nebula California Nebula Heart Nebula Orion Nebula Soul Nebula North America Nebula Cocoon Nebula Gamma Cygni Nebula Veil Nebula Trifid Nebula Crescent Nebula Lagoon Nebula Omega Nebula Eagle Nebula Cat's Paw Nebula Eta Carinae Nebula Crab Nebula Messier 37 Messier 36 Messier 38 Messier 50 Messier 46 Messier 67 Messier 34 Messier 48 Messier 41 Messier 47 Messier 44 Messier 45 Messier 37 Messier 52 Messier 93 Messier 7 Messier 6 Messier 25 Messier 23 Messier 21 Messier 18 Messier 26 Messier 11 Messier 35 NGC 2362 IC 2395 NGC 3114 NGC 3532 IC 1396 IC 2602 NGC 6087 NGC 6025 NGC 3766 NGC 4665 IC 2581 IC 2944 NGC 4755 NGC 3293 NGC 6067 NGC 6193 NGC 6231 NGC 6383 Tr 14 Tr 16 Messier 103 Messier 29 HPer Chi Per Col 228 O Vel Perseus Arm Orion Arm Sagittarius Arm Star cluster Nebula
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.