Pressemeddelelse
Dobbeltmotor for en stjernetåge
5. august 2009
ESO har netop offentliggjort et fantastisk billede af en del af himlen i retning af stjernebilledet Carina (Kølen). Dette slående billede er et mylder af stjerner i alle farver og lysstyrker, hvoraf nogle ses på en baggrund af skyer af støv og gas. Den usædvanlige stjerne i midten, HD 87643, er blevet grundigt undersøgt med flere af ESO’s teleskoper, herunder Very Large Telescope Interferometer (VLTI). Det har vist sig, at stjernen, der er omgivet af en kompleks udstrakt tåge skabt af tidligere voldsomme udslyngninger, har en ledsager. Vekselvirkningerne i dette dobbeltsystem, der er omgivet af en støvskive, er måske den motor, som driver stjernens bemærkelsesværdige tåge.
Det nye billede viser et meget stjernerigt område i retning af Carina-armen i Mælkevejen. Midt i billedet ses stjernen HD 87643, der er et medlem af den eksotiske klasse B[e]-stjerner [1]. Optagelsen er en del af et sæt af observationer, der giver astronomerne det hidtil bedste billede af en B[e]-stjerne.
Billedet blev optaget med Wide Field Imager (WFI), der er monteret på MPG/ESO 2,2 meter teleskopet på La Silla-observatoriet i Chile, som ligger i 2400 meters højde. Billedet viser smukt den udstrakte tåge af gas og støv, der reflekterer lyset fra stjernen. Den centrale stjernes vind har tilsyneladende formet tågen og efterlader lysende, trevlede tråde af gas og støv. En omhyggelig undersøgelse af disse strukturer peger på, at der er regelmæssige udslyngninger af materiale fra stjernen med intervaller på mellem 15 og 50 år.
En gruppe af astronomer ledet af Florentin Millour har studeret stjernen HD 87643 i detaljer ved hjælp af flere af ESO’s teleskoper. Udover WFI, brugte gruppen også ESO’s Very Large Telescope (VLT) på Paranal.
På VLT brugte astronomerne NACO-instrumentet med adaptiv optik, der gør det muligt at optage et billede af en stjerne, der er fri for atmosfærens forstyrrende virkning. For at undersøge objektet nærmere, lavede gruppen derefter et billede med Very Large Telescope Interferometer (VLTI).
Spændvidden for dette sæt af observationer, fra WFI-panoramabilledet til de fine detaljer i VLTI-observationerne, svarer til en zoomfaktor på 60.000 mellem de to yderpunkter. Astronomerne opdagede, at HD 87643 har en ledsager, der ligger i en afstand, som er ca. 50 gange større end Jord-Sol-afstanden og som er indhyllet i en kompakt skal af støv. De to stjerner kredser formentlig om hinanden med en periode på mellem 20 og 50 år. De to stjerner er muligvis også omgivet af en skive af støv.
Tilstedeværelsen af ledsageren kan være forklaringen på de regelmæssige udslyngninger af materiale fra stjernen og dannelsen af tågen: fordi ledsageren bevæger sig i en meget ellipseformet bane, vil den jævnligt komme meget tæt på HD 87643 og dermed udløse en udslyngning.
Noter
[1]: B[e] stjerner er stjerner af sprektaltype B, med emissionslinjer i deres spektre derfor ”e”. De er omgivet af en stor mængde støv.
Mere information
Arbejdet med HD 87643 er blevet offentliggjort i en artikel i Astronomy and Astrophysics: A binary engine fuelling HD 87643’s complex circumstellar environment using AMBER/VLTI imaging, af F. Millour m.fl.
ESO, det Europæiske Syd Observatorium, er den mest fremtrædende internationale astronomi-organisation i Europa og verdens mest produktive astronomiske observatorium. ESO har i dag følgende 14 medlemslande: Belgien, Danmark, Finland, Frankrig, Holland, Italien, Portugal, Schweiz og Storbritannien, Spanien, Sverige, Tjekkiet, Tyskland og Østrig. ESO’s aktiviteter er fokuseret på design, konstruktion og drift af jordbaserede observationsfaciliteter for astronomi for at muliggøre vigtige videnskabelige opdagelser. ESO spiller også en ledende rolle for at fremme og organisere samarbejdet inden for astronomisk forskning. I Chile driver ESO tre unikke observatorier i verdensklasse: La Silla, Paranal og Chajnantor. På Paranal driver ESO Very Large Telescope (VLT), der er verdens mest avancerede astronomiske observatorium til observationer i synligt lys. ESO er den europæiske partner i et revolutionerede astronomisk teleskop kaldet ALMA, det største igangværende astronomiske projekt. ESO planlægger i øjeblikket et 42 meter optisk/nær-infrarødt teleskop kaldet European Extremely Large Telescope (E-ELT), der vil blive ”verdens største øje mod himlen”.
Links
Kontakter
Florentin Millour
Max-Planck Institute for Radio Astronomy
Bonn, Germany
Tel: +49 228 525 188
E-mail: fmillour@mpifr.de
Henri Boffin
ESO
Paranal, Chile
Tel: +49 89 3200 6222
E-mail: hboffin@eso.org
Valeria Foncea
ESO
Chile
Tel: +56 2 463 3123
E-mail: vfoncea@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.: | eso0928da |
| Legacy ID: | PR 28/09 |
| Navn: | HD 87643 |
| Type: | Milky Way : Star : Type : Exotic Milky Way : Nebula |
| Facility: | MPG/ESO 2.2-metre telescope, Very Large Telescope, Very Large Telescope Interferometer |
| Instruments: | AMBER, MIDI, NACO, WFI |
| Science data: | 2009A&A...507..317M |
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