Orion Arm

spiral arms of the Galaxy

The Orion Arm is a minor spiral arm of the Milky Way Galaxy close to the inner edge of which the Sun is located. Its name derives from the fact that the stars closest to the Sun which actually lie within the arm are in the constellation of Orion, about 2,000 light-years away. These include the bright stars of Orion's Belt, Alnilam, Alnitak, and Mintaka. The Orion Arm is also called the Orion Spur or Local Arm.


It is important to recognize that the Orion Arm is not a physical structure but a zone where new stars have been created, by the passage of a density wave, and have subsequently illuminated the interstellar medium around them. The picturesque analogy has been drawn between spiral arms and bands of luminescent plankton churned up in the wake of a ship.