Fanget i en støvfælde
Billedet her, fra Atacama Large Millimeter/submillimeter Array (ALMA) viser V1247 Orionis, som er en ung varm stjerne omgivet af en aktiv ring af gasser og støv - det, som kaldes en circumstellar disc. Skiven ser man her i to dele; en klart afgrænset central ring af stof og så en tyndere halvmåneform længere ude.
Området imellem ringen og halvmånebuen - det, som vi ser som en mørk stribe - formodes at stamme fra en ung planet, som skærer sig vej igennem skiven. På planetens vej omkring stjernen, skaber den områder med højt tryk på hver side af sin bane, lidt i retning af, hvordan et skib danner stævnbølger på vej igennem vandet. Disse højtryksområder kan fungere som beskyttede områder der, hvor der sker ny planetdannelse: i områderne fanges støvpartikler i millioner af år, og det giver dem tid til at klumpe sig sammen og vokse til planeter.
ALMAs gode opløsningsevne gør det muligt for astronomerne at studere detaljerne lige netop i sådan en støvfælde for første gang. På billedet ser man ikke blot den halvmåneformede støvfælde lige udenfor den mørke stribe, men også områder med overskud af støv inde i ringen. Disse tyder på, at der findes en yderligere støvfælde indenfor den kommende planets bane. Og det er altsammen i tråd med tidligere computerberegninger.
De støvfælder er en mulig løsning på et større problem i de nuværende teorier for planetdannelsen. I dem forudsiges det, at partikler burde drive ind til den centrale stjerne, for der at blive ødelagt før de får tid til at vokse sig til den størrelse, som planetesimaler må have (det, som kaldes 'radial drift problem').
Kilde:ALMA (ESO/NAOJ/NRAO)/S. Kraus (University of Exeter, UK)
Om billedet
| Id: | potw1742a |
| Sprog: | da |
| Type: | Observation |
| Udgivelsesdato: | 16. oktober 2017 06:00 |
| Størrelse: | 2000 x 2000 px |
Om objektet
| Navn: | V1247 Orionis |
| Type: | Milky Way : Star : Circumstellar Material : Disk : Protoplanetary |
| Constellation: | Orion |
Baggrundsbilleder
Koordinater
| Position (RA): | 5 38 5.25 |
| Position (Dec): | -1° 15' 21.70" |
| Field of view: | 0.03 x 0.03 arcminutes |
| Orientering: | Nord er -0.0° venstre fra lodret |
Farver & filtre
| Bånd | Bølgelængde | Teleskop |
|---|---|---|
| Milimeter H | 870 μm | Atacama Large Millimeter/submillimeter Array Band 7 |
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