Sagittarius Arm

Observed structure of the Milky Way's spiral arms

The Sagittarius Arm (also known as Sagittarius-Carina Arm, labeled -I) is generally thought to be one of the spiral arms of our home galaxy, the Milky Way. Each spiral arm is a long, diffuse curving streamer of stars that radiates out from the galactic center. These gigantic structures are often composed of billions of stars, and Sagittarius is one of the largest arms in our galaxy.

The Milky Way is a barred spiral galaxy, consisting of a central crossbar from which several spiral arms radiate outwards. The Sagittarius Arm's innermost end connects to one of the ends of this central bar, making it one of the two major spiral arms of the galaxy. The other large arm is the Cygnus Arm.

The dense, inner arm of Sagittarius is located between the Scutum-Crux Arm and the Orion Arm (the Orion arm is marked as the Local Spur on the galactic map, and Orion also contains our sun). It is named for its proximity to the Sagittarius constellation as seen in the night sky from Earth, in the direction of the galactic center.

The Sagittarius Arm is divided into two parts. Curving outward from the galaxy's central bar is the Sagittarius Arm (Sagittarius bar), which further outward becomes the Carina arm.

Minor arm

Recently, it has been suggested that the Sagittarius Arm is a minor arm, along with the Cygnus Arm. These two appear to be mostly concentrations of gas, sparsley sprinkled with pockets of newly formed stars.^[1]

Visible Objects

A number of Messier objects and other objects visible through an amateur's telescope or binoculars are found in the Sagittarius Arm:

• M8, the Lagoon Nebula
• M11, the Wild Duck Cluster
• M16, the Eagle Nebula
• M17, the Omega Nebula
• Open Cluster M18
• M20, the Trifid Nebula
• Open Cluster M21
• M24, the Sagittarius Star Cloud
• Open Cluster M26
• Globular Cluster M55
• NGC 3372, the Carina Nebula

Other resources

See also

• List of Messier objects

References

External links

• http://members.fcac.org/~sol/chview/chv5.htm
• http://skyandtelescope.com/mm_images/6829.jpg
• Messier Objects in the Milky Way (SEDS)

v • d • e The Milky Way Location Universe · Virgo Supercluster · Local Group Galactic core Center of the Milky Way Spiral arms Sagittarius-Carina · Scutum-Crux · Norma-Cygnus · Perseus · Orion Satellite galaxies Dwarves Boötes · Canes Venatici · Canis Major · Carina · Draco · Fornax · Leo I · Leo II · Phoenix · Sagittarius Elliptical · Sculptor · Segue 1 · Sextans Spheroidal · Ursa Major I · Ursa Major II · Ursa Minor Other Large Magellanic Cloud · Magellanic Stream · Monoceros Ring · Small Magellanic Cloud · Virgo Stream · Willman 1

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