An Aligned Stream of Low-Metallicity Clusters in the Halo of the Milky Way

@article{Yoon2002AnAS,
  title={An Aligned Stream of Low-Metallicity Clusters in the Halo of the Milky Way},
  author={Suk-Jin Yoon and Young-Wook Lee},
  journal={Science},
  year={2002},
  volume={297},
  pages={578 - 581}
}
One of the long-standing problems in modern astronomy is the curious division of Galactic globular clusters, the “Oosterhoff dichotomy,” according to the properties of their RR Lyrae stars. Here, we find that most of the lowest metallicity ([Fe/H] < –2.0) clusters, which are essential to an understanding of this phenomenon, display a planar alignment in the outer halo. This alignment, combined with evidence from kinematics and stellar population, indicates a captured origin from a satellite… 

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