Håndvægttågen
Håndvægttågen - også kendt som Messier 27 eller NGC 6853 - er en typisk planetarisk tåge og den ligger i stjernebilledet Vulpecula (Ræven).
Afstanden er temmelig usikker, men menes at være omkring 1.200 lysår.
Den blev først beskrevet af den franske astronom og kometjæger Charles Messier, der fandt den i 1764 og inkluderede den som nummer 27 i sin berømte liste af udstrakte himmelobjekter. På trods af sin klassebetegnelse, har Håndvægttågen intet at gøre med planeter.
Den består af meget tynd gas, der er blevet afstødt fra den varme centrale stjerne (klart synlig på dette billede), som nu befinder sig i et af de sidste evolutionære stadier.
Gasatomerne i tågen er eksiterede (opvarmet) af den intense ultraviolette stråling fra stjernen og udsender en del lys i bestemte bølgelængder.
Dette billede er det smukke biprodukt af en teknisk test af nogle af FORS1s smalbåndede optiske interferensfiltre, der kun lader lys i et meget snævert bølgelængdeområde at passere og bruges til at isolere lys udsendt af bestemte atomer og ioner.
I dette tre-farvede sammensatte billede, blev en kort eksponering først lavet gennem et bredbånd filter for at registrere blåt lys fra tågen.
Det blev derefter kombineret med eksponeringer gennem to interferensfiltre for at fange lyset af dobbeltioniserede iltatomer og atomar brint.
billederne blev så farvekodet "blå", "grøn" og "røde" henholdsvis og derefter kombineret til dette billede, der viser strukturen af tågen i "tilnærmelsesvis sande" farver.
Billedet er sammensat af tre farver baseret på to interferens ([oiii] ved 501 nm og 6 nm FWHM - 5 min eksponeringstid, H-alpha ved 656 nm og 6 nm FWHM - 5 min) og en bredbåndsforbindelse ( Bessell B ved 429 nm og 88 nm FWHM, 30 sek) filtrerede billeder, taget den 28. september 1998 under middelmådige seeing forhold (0,8 buesekunder).
CCD-kameraet har 2048 x 2048 pixels, der hver dækker 24 x 24 um og på himlen svarer det til 6,8 x 6,8 bueminutter og 3,5 x 3,9 bueminutter hhv.
Nord er op; Øst er mod venstre.
ESO/I. Appenzeller, W. Seifert, O. Stahl, M. Zamani
Om billedet
| Id: | eso9846a |
| Sprog: | da |
| Type: | Observation |
| Udgivelsesdato: | 7. oktober 1998 |
| Relaterede pressemeddelelser: | eso9846 |
| Størrelse: | 2044 x 2042 px |
Om objektet
| Navn: | Dumbbell Nebula, M 27, Messier 27, NGC 6853 |
| Type: | Milky Way : Nebula : Type : Planetary |
| Afstand: | 1200 lysår |
| Constellation: | Vulpecula |
Billedformater
Baggrundsbilleder
Koordinater
| Position (RA): | 19 59 36.41 |
| Position (Dec): | 22° 43' 16.00" |
| Field of view: | 6.76 x 6.82 arcminutes |
| Orientering: | Nord er 0.0° venstre fra lodret |
Farver & filtre
| Bånd | Bølgelængde | Teleskop |
|---|---|---|
| Optisk u | 361 nm | Very Large Telescope FORS1 |
| Optisk B | 429 nm | Very Large Telescope FORS1 |
| Optisk Oiii | 501 nm | Very Large Telescope FORS1 |
| Optisk HeII | 472 nm | Very Large Telescope FORS1 |
| Optisk R | 655 nm | Very Large Telescope FORS1 |
| Optisk H-alpha | 656 nm | Very Large Telescope FORS1 |
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