Pressemeddelelse
Et flygtigt øjeblik i tiden
Det sidste åndedrag fra en døende stjerne indfanget i European Southern Observatorys billedprojekt Cosmic Gems.
22. januar 2019
Kun i kort tid endnu kan vi se den svage spøgelsesagtige glød fra den planetariske tåge ESO 577-24 - et øjeblik i astronomisk tidsmål; bare 10 000 år. Boblen af lysende ioniseret gas - som er en døende stjernes sidste gisp, samt selve stjernen i centrum, kan stadig ses med ESOs Very Large Telescope. Men langsomt forsvinder det hele. Boblen udvider sig og bliver svagere med tiden.
Vi har at gøre med en skal eller boble af meget tynd gas, som spreder sig udad i rummet - den planetariske tåge ESO 577-24, som har hovedrollen på billedet her[1]. Tågen er resterne fra en død kæmpestjerne, som har kastet sine ydre lag af sig, så der tilbage er en lille, men meget varm dværgstjerne. Den skrumpede stjernerest køler langsomt ned, bliver svagere, og vil slutte sine dage som bare en afglans af, hvad der en gang var en enorm rød kæmpestjerne.
Røde kæmper er stjerner i slutningen af deres levetid. De har opbrugt deres brændstof; hydrogen i kernen, og de er skrumpet under tyngdekraftens ubønhørlige pres. Men når den røde kæmpe skrumper, vil den enorme trykstigning i det indre igen tænde kerneprocesserne i stjernens kerne. Det får så igen energiproduktionen til at stige brat, så stjernens ydre lag bliver slynget ud i tomrummet i form af en kraftig stjernevind. Stjernens glødende kerne udsender ultraviolet stråling, som er kraftig nok til at ionisere de tynde lag af gas, så de lyser op, mens de fjerner sig fra stjernen. Det er det, vi ser som den planetariske tåge. Den sidste svage hilsen fra en gammel stjerne, som er ved at slutte sit livsløb[2].
Denne smukke planetariske tåge blev opdaget undervejs i den gennemmønstring af himlen, som kaldes National Geographic Society — Palomar Observatory Sky Survey i 1950'erne, og den blev optaget i værket Abell Catalogue of Planetary Nebulae i 1966 [3]. Det spøgelsesagtige lys fra ESO 577-24 kan kun ses i kraftige teleskoper, for afstanden er omkring 1400 lysår. I takt med at dværgstjernen køler ned, vil tågen fortsat udvide sig, indtil den langsomt svinder ud af syne.
Billedet her af ESO 577-24 er optaget i forbindelse med ESO Cosmic Gems Programme, hvor formålet er at optage billeder af interessante, spændende eller blot smukke objekter med ESOs teleskoper til glæde for uddannelse og formidling overfor offentligheden. I programmet bruger vi observationstid, som ikke kan bruges til videnskabelige observationer, men alle data bliver også lagt ud til brug for de professionelle astronomer i det, som kaldes ESO Science Archive.
Noter
[1] Planetariske tåger blev først observeret af astronomer i det 18 århundrede, og for dem, med datidens ringere teleskoper, lignede objekterne planeterne i Solsystemet - deraf navnet.
[2] På det tidspunkt, hvor vores egen Sol begynder at udvikle sig til en rød kæmpestjerne, har den nået den adstadige alder af 10 milliarder år. Der er dog ingen grund til panik - for tiden er Solen blot 5 milliarder år gammel, så hvad det angår kan man roligt investere i fast ejendom.
[3] Astronomiske objekter har ofte mange forskellige officielle navne, taget fra de forskellige kataloger. Objektet her hedder i Abell Catalogue of Planetary Nebulae PN A66 36.
Mere information
ESO er den fremmeste fællesnationale astronomiorganisation i Europa, og verdens langt mest produktive jordbaserede astronomiske observatorium. 16 lande er med i ESO: Belgien, Danmark, Finland, Frankrig, Irland, Italien, Nederlandene, Polen, Portugal, Spanien, Sverige, Schweiz, Storbritannien, Tjekkiet, Tyskland og Østrig, og desuden værtsnationen Chile. Australien er med som strategisk partner. ESO har et ambitiøst program, som gør det muligt for astronomer at gøre vigtige videnskabelige opdagelser. Programmet har focus på design, konstruktion og drift af stærke jordbaserede observatorier. Desuden har ESO en ledende rolle i formidling og organisering af samarbejde omkring astronomisk forskning. ESO driver tre enestående observatorier i verdensklasse i Chile: La Silla, Paranal og Chajnantor. På Paranal driver ESO VLT, Very Large Telescope, som er verdens mest avancerede observatorium for synligt lys, samt to oversigtsteleskoper. VISTA, som observerer i infrarødt, er verdens største oversigtsteleskop, og VLT Survey Teleskopet er det største teleskop bygget til at overvåge himlen i synligt lys. ESO er en af de største partnere i ALMA, som er det største eksisterende astronomiprojekt. For tiden bygges ELT, et 39 m optisk og nærinfrarødt teleskop på Cerro Armazones, tæt ved Paranal. Det bliver "verdens største himmeløje".
Links
Kontakter
Calum Turner
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
E-mail: pio@eso.org
Ole J. Knudsen (Pressekontakt Danmark)
ESOs formidlingsnetværk
og Aarhus Space Centre, Aarhus Universitet
Aarhus, Danmark
Tel: +45 8715 5597
E-mail: eson-denmark@eso.org
Om pressemeddelelsen
| Pressemeddelelse nr.: | eso1902da |
| Navn: | ESO 577-24 |
| Type: | Milky Way : Nebula : Type : Planetary |
| Facility: | Very Large Telescope |
| Instruments: | FORS2 |
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