Meddelande
ALMA gör de mest högupplösta observationerna hittills
15 november 2023
Atacama Large Millimeter/submillimeter Array (ALMA), där ESO är en partner, har uppnått de mest högupplösta observationerna sedan antennsystemet togs i bruk. Under ett tekniskt test, där experter från Joint ALMA Observatory (JAO), National Astronomical Observatory of Japan (NAOJ), National Radio Astronomy Observatory (NRAO) i USA och ESO deltog, avbildades en gammal jättestjärna med en upplösning av 5 millibågsekunder. Det motsvarar storleken på en 10 meter lång buss sedd på månens yta.
ALMA består av 66 antenner som kan placeras i olika positioner på högplatån Chajnantor i Chile. Varje antenn är utrustad med en mottagare för radiovågor i olika frekvensområden eller band. ALMA:s upplösning ökar både med ökande avstånd mellan antennerna och med strålningens frekvens.
De nya observationerna gjordes med ALMA i sin mest utspridda konfiguration, där det största avståndet mellan antennerna är 16 km. De gjordes med Band 10-mottagarna som är känsliga för frekvenser upp till 950 GHz, vilket är den högsta möjliga frekvensen för antennerna.
Eftersom observationerna pressade ALMA:s kapacitet till det yttersta var de otroligt svåra att genomföra. Band 10-mottagarna har varit tillgängliga på ALMA sedan 2014, men astronomerna var tvungna att invänta en ny kalibreringsteknik, “band-till-band”, för att göra observationerna. Dessa skedde 2021 under ett test där jättestjärnan R Leporis observerades tillsammans med en (på himlen) närbelägen galaxkärna. Resultaten publiceras i dag i tidskriften Astrophysical Journal.
Resultatet har erhållits tack vare ett betydande stöd från ESO-personal, erfarenheter från tidigare observationer och utvecklingen av den nya kalibreringstekniken.
Mer information
Forskningsresultaten presenteras i artikeln “ALMA High-frequency Long Baseline Campaign in 2021: Highest Angular Resolution Submillimeter Wave Images for the Carbon-rich Star R Lep” (doi:10.3847/1538-4357/acf619) i tidskriften Astrophysical Journal.
Forskarlaget utgörs av Y. Asaki (JAO; NAOJ; SOKENDAI), L. Maud (ESO; Leiden University), H. Francke (JAO), H. Nagai (NAOJ), D. Petry (ESO), E. B. Fomalont (NRAO), E. Humphreys (JAO; ESO), A. M. S. Richards (University of Manchester), K. T. Wong (IRAM; Uppsala University), W. Dent (JAO), A. Hirota (JAO; NAOJ), J. M. Fernandez (Lowell Observatory), S. Takahashi (NAOJ), och A. S. Hales (JAO; NRAO).
En tidigare teknisk studie som ledde till kampanjen 2021 beskrivs i artikeln “ALMA High-frequency Long-baseline Campaign in 2019: Band 9 and 10 In-band and Band-to-band Observations Using ALMA's Longest Baselines”, som publicerades Astrophysical Journal i augusti 2023 (doi: 10.3847/1538-4365/acd6f1).
ALMA är ett partnerskap mellan ESO (som representerar dess medlemsstater), NSF (USA) och NINS (Japan), tillsammans med NRC (Kanada), NSTC och ASIAA (Taiwan) och KASI (Sydkorea) i samarbete med republiken Chile. Joint ALMA Observatory drivs av ESO, AUI/NRAO och NOAJ.
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