Helmi stream
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][3] 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.[2]
Extragalactic planet
[edit]The Helmi stream was home to the first discovered 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
[edit]References
[edit]- ^ a b Scientific American, "Extragalactic Expat: Newfound Exoplanet Likely Came from Another Galaxy", John Matson , 18 November 2010
- ^ a b "Amina Helmi, the "archeologist of the Milky Way," explains how our own galaxy could unlock the mystery of dark matter". FBBVA. 12 December 2017. Retrieved 7 November 2019.
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.
- ^ Skibba, Ramin (10 June 2021). "A galactic archaeologist digs into the Milky Way's history". Knowable Magazine. doi:10.1146/knowable-060921-1. S2CID 236290725. Retrieved 4 August 2022.
- ^ 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:1401.0517. Bibcode:2014A&A...562A.129J. doi:10.1051/0004-6361/201322132. S2CID 55365608.
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