Rusty old stars: a source of the missing interstellar iron

  title={Rusty old stars: a source of the missing interstellar iron},
  author={Iain McDonald and G. C. Sloan and Albert A. Zijlstra and Noriyuki Matsunaga and Mikako Matsuura and Kathleen E. Kraemer and Jeronimo Bernard-Salas and Andrew J. W. Markwick},
Iron, the universe’s most abundant refractory element, is highly depleted in both circumstellar and interstellar environments, meaning it exists in solid form. The nature of this solid is unknown. In this Letter, we provide evidence that metallic iron grains are present around oxygen-rich asymptotic giant branch stars, where it is observationally manifest as a featureless mid-infrared excess. This identification is made using Spitzer Space Telescope observations of evolved globular cluster… 

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