Helmi star current

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The Helmi Sternstrom (after Amina Helmi , see below), also short Helmi-Strom , also H99 streams , is a group of low-metal stars in the outer areas of the Milky Way , which are characterized by a special movement pattern: they have eccentric orbits around the galactic center with a minimum of about 7 kpc ( kiloparsec ) to a maximum of about 16 kpc from the latter; they reach distances from the galactic plane of up to 13 kpc.

According to the work of a research group led by Amina Helmi, which is based on the precise star words supplied by the Hipparcos satellite , these stars once belonged to a dwarf galaxy that orbited the Milky Way, was dissolved by tidal forces and converted into a stellar current. According to a model calculation , this happened about 6 to 9 billion years ago.

The star HIP 13044 belongs to the Helmi Sternstrom . A research group (Setiawan et al.) Described indications of the existence of an exoplanet around this star in a paper published in Science in 2010 . A quote in the ESO press release was sometimes misinterpreted by the general press and therefore wrongly received as the discovery of an "extragalactic planet" instead of an exoplanet of extragalactic origin. However, the existence of this exoplanet was not confirmed in a new analysis of the observation data published in 2014.

Individual evidence

  1. ↑ a b c Amanda A. Kepley, Heather L. Morrison, Amina Helmi, TD Kinman, Jeffrey Van Duyne, John C. Martin, Paul Harding, John E. Norris, Kenneth C. Freeman: Halo Star Streams in the Solar Neighborhood . In: Astronomical Journal . 134, November 6, 2006, pp. 1579-1595. arxiv : 0707.4477 . doi : 10.1086 / 521429 . Retrieved April 25, 2015.
  2. ↑ Amina Helmi, Simon DM White, P. Tim de Zeeuw, HongSheng Zhao: Debris streams in the solar neighborhood as relicts from the formation of the Milky Way . In: Nature . 402, June 18, 1999, pp. 53-55. doi : 10.1038 / 46980 .
  3. ↑ Johny Setiawan, Rainer J. Klement, Thomas Henning, Hans-Walter Rix, Boyke Rochau, Jens Rodmann, Tim Schulze-Hartung: A Giant Planet Around a Metal-poor Star of Extragalactic Origin. (PDF) ESO, November 18, 2010, accessed April 26, 2015 . ( doi : 10.1126 / science.1193342 )
  4. ↑ A planet from a strange galaxy discovered. ESO Science News Release, November 18, 2010, accessed April 29, 2015 .
  5. ↑ For example: Kerstin Holzheimer: Extragalactic Planet discovered. Frankfurter Rundschau, November 19, 2010, accessed on April 26, 2015 .
  6. ↑ MI Jones, JS Jenkins: No evidence of the planet orbiting the extremely metal-poor extragalactic star HIP 13044 . In: Astronomy & Astrophysics . 562, January 2, 2014, p. A129. arxiv : 1401.0517 . bibcode : 2014A & A ... 562A.129J . doi : 10.1051 / 0004-6361 / 201322132 .