Galactic Archaeology

Exposing an act of galactic cannibalism

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Science  07 Aug 2015:
Vol. 349, Issue 6248, pp. 599
DOI: 10.1126/science.349.6248.599-a

Artist's depiction of the Sagittarius Dwarf Tidal Stream encircling the Milky Way galaxy


Our Milky Way galaxy contains two streams of stars that have been stripped by its gravity from the neighboring Sagittarius Dwarf Spheroidal Galaxy (Sgr dSph). de Boer et al. have disentangled the streams from the surrounding Milky Way and analyzed their star formation history. No stars are younger than 6 billion years old, indicating when they were ripped from the Sgr dSph. The streams also reveal how the stars originally formed in the Sgr dSph, including the moment when type Ia supernovae began enriching the galaxy. This galactic archaeology will help us understand how the Milky Way grew by consuming smaller galaxies.

Mon. Not. R. Astron. Soc. 451, 3489 (2015).

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