Sagittarius Stream

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In astronomy, the Sagittarius Stream is a long, complex, structure made of stars that wrap around the Milky Way galaxy in an almost polar orbit. It consists of tidally stripped stars from the Sagittarius Dwarf Elliptical Galaxy resulting from the process of merging with the Milky Way over a period of billions of years.


This stellar stream was originally proposed in 1995 by Donald Lynden-Bell after analyzing the distribution of globular clusters in the Milky Way.[1] The actual structure was identified by Newberg et al. (2002)[2] and Majewski et al. (2003)[3] using data from the 2MASS and SDSS surveys. In 2006, Belokurov and his collaborators[4] found that the Sagittarius Stream has two branches.

Association with spiral arm layering[edit]

The shredding apart of a large intruding collection of stars in the indefinite past appears to have sent oscillations analogous to sound waves through the Milky Way spiral arm structure. The effects of the oscillations are observed today as vertically stacked layers of alternately denser and sparser star distributions above and below the Solar System. Presently, the Sagittarius Stream is positioned relative to the observed layers[5] such that its progenitor, the Sagittarius Dwarf Elliptical Galaxy, is the strongest candidate intruder whose wake left behind the disturbance in the spiral arms.


  1. ^ Lynden-Bell, R. M.; Lynden-Bell, D. (July 1995). "Ghostly streams from the formation of the Galaxy's halo". Monthly Notices of the Royal Astronomical Society. 275 (2): 429–442. Bibcode:1995MNRAS.275..429L. doi:10.1093/mnras/275.2.429. 
  2. ^ The Ghost of Sagittarius and Lumps in the Halo of the Milky Way
  3. ^ A Two Micron All Sky Survey View of the Sagittarius Dwarf Galaxy. I. Morphology of the Sagittarius Core and Tidal Arms
  4. ^ The Field of Streams: Sagittarius and Its Siblings
  5. ^ Yanny, Brian; Gardner,Susan (Sep 2013). "The Stellar Number Density Distribution in the Local Solar Neighborhood is North-South Asymmetric". arXiv:1309.2300free to read. 

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