Helmi stream

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The Helmi stream is a stellar stream of the Milky Way galaxy. It started as a dwarf galaxy, now absorbed by the Milky Way as a stream. It was discovered in 1999, is formed of old stars deficient in heavy elements and has a mass of 10 to 100 million solar masses. It was absorbed by the Milky Way some 6 to 9 billion years ago.[1]

Extragalactic planet[edit]

The Helmi stream was home to the first planet purportedly of extragalactic origin, orbiting the star HIP 13044.[1] Unfortunately, further analysis of radial velocity data failed to confirm the discovery.[2]

See also[edit]


  1. ^ a b Scientific American, "Extragalactic Expat: Newfound Exoplanet Likely Came from Another Galaxy", John Matson , 18 November 2010
  2. ^ Jones, M. I.; Jenkins, J. S. (2014). "No evidence of the planet orbiting the extremely metal-poor extragalactic star HIP 13044". Astronomy & Astrophysics. 562: id.A129. arXiv:1401.0517Freely accessible. Bibcode:2014A&A...562A.129J. doi:10.1051/0004-6361/201322132.