Far 3 kpc Arm

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Artist's conception of the spiral structure of the Milky Way with two major stellar arms and a central bar. In this image the Far 3 kpc Arm is located near the center, above and to the left of the bulge.

The Far 3 kpc Arm was discovered in 2008 by astronomer Tom Dame (Harvard-Smithsonian CfA), while preparing a talk on the Galaxy's spiral arms for a meeting of the 212th American Astronomical Society. It is one of Milky Way's spiral arms and it is located in the first galactic quadrant at a distance of 3 kpc (about 10,000 ly) from the galactic center. Along with the Near 3 kpc Arm whose existence is known since the mid-1950s, the counterpart inner arms establish our Galaxy's simple symmetry.[1]

Tom Dame and collaborator Patrick Thaddeus analyzed data obtained using a 1.2-meter-diameter millimeter-wave telescope located at Cerro Tololo Inter-American Observatory (CTIO) in Chile. They detected the presence of the spiral arm in a CO survey and later confirmed their discovery using 21-centimeter radio measurements of atomic hydrogen collected by colleagues in Australia.[2][3]


  1. ^ Nemiroff, R.; Bonnell, J., eds. (11 July 2008). "The Far 3kpc Arm". Astronomy Picture of the Day. NASA.
  2. ^ Milky Way's Inner Beauty Revealed, Press Release Harvard-Smithsonian Center for Astrophysics, 2008
  3. ^ A New Spiral Arm of the Galaxy: The Far 3-Kpc Arm, T. M. Dame, P. Thaddeus, ApJ Letters, 2008