Nemesis (hvězda)

Nemesis („hvězda smrti“, podle řecké bohyně pomsty a odplaty Nemesis) je astronomický koncept, který vzešel z pozorování domnělé cykličnosti masových vymírání v dějinách života na Zemi, odkrytých v geologickém záznamu.[1] Tento koncept je jednou z hypotéz, která má toto pozorované vymírání vysvětlit. Podle paleontologů Davida M. Raupa a Jacka Sepkoskiho, kteří s ideou v roce 1983 přišli, může za pravidelně se opakující vymírání s periodou kolem 26 milionů let neznámá hvězda, která obíhá kolem našeho Slunce a v těchto obdobích vždy gravitačně způsobí přísun asteroidů a komet, které se pak se Zemí mohou srazit. Geofyzik Luis Walter Alvarez a jeho spolupracovníci spočítali, že by se muselo jednat o hnědého nebo červeného trpaslíka ve vzdálenosti asi 1,5–3 světelných let od Slunce. Dosud však žádná takto blízká hvězda nebyla nalezena a dnes se od konceptu Nemesis upouští. Pravděpodobně žádná taková temná hvězda neexistuje, a tak nejbližší hvězdou zůstává jiný červený trpaslík Proxima Centauri ve vzdálenosti 4,22 světelného roku. O Nemesis nicméně vzniklo množství románů a filmových či komiksových zpracování. Perioda v záznamech ale existuje.[2] Podobnou je hypotéza Šiva s periodou přibližně 30 milionů let, kterou navrhl Michael Rampino. Kombinace dvou period pak má objasňovat změny ve vulkanismu a tak i vymírání.[3]

Odkazy

Reference

  1. ↑ SOCHA, Vladimír. Neviditelná Nemesis: Kde vězí tajemná hvězda smrti?. 100+1 zahraniční zajímavost [online]. 2020-09-10 [cit. 2022-01-22]. Dostupné online. 
  2. ↑ MELOTT, Adrian L.; BAMBACH, Richard K. Nemesis reconsidered: Nemesis reconsidered. S. L99–L102. Monthly Notices of the Royal Astronomical Society: Letters [online]. 2010-09-01. Roč. 407, čís. 1, s. L99–L102. Dostupné online. DOI 10.1111/j.1745-3933.2010.00913.x. (anglicky) 
  3. ↑ Lethal climate change millions of years ago was due to volcanic eruptions, scientists conclude. phys.org [online]. [cit. 2023-10-10]. Dostupné online. 

Literatura

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