En himmelsk bedragare
I rymden är inte allt vad det verkar vara. Denna veckas bild visar nebulosan Sh2-46, även kallad Gum 80, belägen ungefär 6000 ljusår bort. De starka röda nyanserna i Sh2-46 må vara vackra, men de döljer en bedragare.
Den ljusa blåvita stjärnan i mitten av bilden är HD 165319, en stjärna av O-typ, som en av de ljusaste men också sällsyntaste typerna av stjärnor i universum. Stjärnan är till stor del ansvarig för de slående röda tonerna runtomkring, som orsakas av jonisering av väteatomerna i nebulosan. Denna stjärna borde dock inte finnas här.
Astronomer tror att denna stjärna föddes någon annanstans: i den närliggande Örnnebulosan. Örnnebulosan, som ligger i svanssektionen av stjärnbilden Ormen, är nämligen ett rikt stjärnbildningsområde. När dess stjärnor väl är födda binds de av gravitationen och skapar en gigantisk öppen stjärnhop. Ibland sliter sig dock någon av dem loss och ger sig ut på ett ensamt uppdrag genom rymden, som kan leda till att de infiltrerar andra orelaterade nebulosor. En bågchock vid HD 165319 verkar indikera att stjärnan för närvarande rusar genom Sh2-46 med hög hastighet. Kanske kommer nebulosan att se annorlunda ut när stjärnan väl lämnar den bakom sig…
Denna mycket detaljerade bild av Sh2-46 togs av VLT Survey Telescope (VST), som studerar himlen i synligt ljus. VST, som för närvarande ägs av INAF, det italienska nationella institutet för astrofysik, är beläget vid ESO:s Paranalobservatorium i Chile. Denna bild släpps med anledning av 100-årsjubileet för planetariet, och visas bland annat på kupolen i ESO Supernova Planetarium & Visitor Centre.
Länk
Källa:ESO/VPHAS+ team
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