Helmi stream explained
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]
The stream was named after Amina Helmi, who discovered this stellar stream after noticing this group of stars all moving at the same speed and in the same direction.[2] The Helmi Stream discovery affirmed theories that the merging of galaxies played a significant role in creating the giant structures of the Milky Way galaxy.[3]
Extragalactic planet
The Helmi stream was home to the first planet purportedly of extragalactic origin, orbiting the star HIP 13044.[1] Further analysis of radial velocity data failed to confirm the discovery.[4]
See also
Notes and References
- Scientific American, "Extragalactic Expat: Newfound Exoplanet Likely Came from Another Galaxy", John Matson, 18 November 2010
- Skibba . Ramin . A galactic archaeologist digs into the Milky Way's history . Knowable Magazine . 10 June 2021 . 10.1146/knowable-060921-1 . 236290725 . 4 August 2022. free .
- Web site: Amina Helmi, the "archeologist of the Milky Way," explains how our own galaxy could unlock the mystery of dark matter. 2017-12-12 . FBBVA . en . 2019-11-07 . "The idea had already been mooted that the merging of small galaxies could have played a major part in forming today’s giant structures. Helmi developed the tools that were able to test this hypothesis and confirm that it held true, at least for the Milky Way. " .
- Jones, M. I. . Jenkins, J. S. . No evidence of the planet orbiting the extremely metal-poor extragalactic star HIP 13044. Astronomy & Astrophysics. 562. id.A129. 2014. 2014A&A...562A.129J. 10.1051/0004-6361/201322132. 1401.0517. 55365608 .
