Tiedote

ALMA linkittyy muiden observatorioiden kanssa luodakseen Maan kokoisen virtuaalisen teleskoopin

10. marraskuuta 2015

Atacama Large Millimeter/submillimeter Array eli ALMA tehostaa toimintakykyään ja laajentaa ominaisuuksiaan linkittymällä muiden radioteleskooppien kanssa Euroopassa ja Pohjois-Amerikassa hyvin pitkän perusviivan interferometrian (VLBI) havaintojen kautta.

VLBI:ssä kahden tai useamman teleskoopin havainnot yhdistetään yhdeksi virtuaaliseksi teleskoopiksi, missä teleskoopit ovat hyvin kaukana toisistaan. Viimeisimmässä testissä ALMA yhdessä muiden teleskooppien kanssa muodostivat Maan kokoisen teleskoopin mahdollistaen poikkeuksellisen hyvän erotuskyvyn.

Näiden testien tekeminen on keskeinen vaihe, jotta ALMA saadaan liitettyä mukaan "Event Horizon Telescope (EHT)"-verkostoon, mikä on maailmanlaajuinen millimetrin aallonpituudella havaitsevien teleskooppien verkosto. Tämä pystyy havaitsemaan ja tutkimaan Linnunradan keskustassa olevaa supermassivista mustaa-aukkoa ennennäkemättömän yksityiskohtaisesti.

ALMA:n osallistuessa aikaisempiin VLBI havaintoihin se täytyi ensin muuttaa "vaiheistettu verkosto" (phased array [1]) tyyppiseksi havaintolaitteeksi. Nyt käytössä oleva ALMA:n versio mahdollistaa 66 antennin toimimisen halkaisijaltaan 85 metrin radioteleskooppina, mikä puolestaan on osa paljon suurempaa VLBI teleskooppia.

Ensimmäinen testi ALMA:n mahdollisuuksista VLBI havaintoihin tehtiin 13.1.2015, kun ALMA linkittyi onnistuneesti "Atacama Pathfinder Experiment (APEX)"-teleskoopin kanssa, mikä sijaitsee noin kahden kilometrin etäisyydellä ALMA-verkoston keskipisteestä.

30.3.2015 ALMA kurkottautui paljon kauemmas linkittymällä "Institut de Radioastronomie Millimetrique’s (IRAM)"-instituutin Etelä-Espanjan Sierra Nevadassa olevan 30 metrin radioteleskoopin kanssa. Radioteleskoopit havaitsivat samanaikaisesti kirkasta kvasaaria 3C 273 [2]. Näiden havaintojen data yhdistettin yhdeksi havainnoksi, jolloin saavutettiin 34 mikrokaarisekunnin erotuskyky. Tämä vastaa alle kymmenen senttimetrin välimatkaa Kuun pinnalla Maasta katsottuna tai alle puolta valovuotta kvasaarin 2.5 miljardin valovuoden etäisyydellä.

Viimeisin VLBI havaintokampanja tehtiin 1–3.8.2015 käyttämällä kuutta National Radio Astronomy observatorion (NRAO) VLBA-antennia [3]. Tämä yhdistetty havaintolaite muodosti virtuaalisen Maan kokoisen teleskoopin ja se havaitsi kvasaaria 3C 454.3, mikä on yksi taivaan kirkkaimmista radiolähteistä, vaikka se sijaitsee 1.8 miljardin valovuoden etäisyydellä. Tämä data prosessointiin ensiksi NRAO:ssa ja MIT-Haystack:issä Yhdysvalloissa ja jatkokäsittely tehtiin Max Planck instituutissa (MPIfR) Saksassa Bonnissa.

Nämä uudet havainnot ovat askel kohti ALMA:n interferometrisia havaintoja osana globaalia mm-VLBI verkostoa ja "Event Horizon"-teleskooppia, missä ALMA on suurin ja herkin mittalaite. ALMA:n mukaantulo millimetrialueen VLBI-mittauksiin kasvattaa olemassaolevien VLBI-verkostojen herkkyyttä ja kyvykkyyttä kertaluvun suuruusluokan verran.

Lisähuomioita

[1] Seuraavat ryhmät ja instituutit osallistuivat "ALMA Phasing"-projektiin: National Radio Astronomy Observatory (USA), Academia Sinica Institute of Astronomy and Astrophysics (Taiwan), National Astronomical Observatory of Japan, Smithsonian Astrophysical Observatory (USA), MIT Haystack (USA), MPIfR (Bonn, Saksa), Onsala Space Observatory (Ruotsi), Universidad de Concepcion (Chile) ja Joint ALMA Observatory.

[2] Maaliskuun havainnot tehtiin EHT:n havaintokampanjan aikana 1.3 mm:n aallonpituudella.

[3] VLBA on eri puolilla Yhdysvaltoja Hawaijista St. Croixiin olevien kymmenen antennin kokoelma. Tähän havaintoon käytettiin kuutta radioteleskooppia ja havainnossa käytetty aallonpituus oli 3 mm.

Yhteystiedot

Richard Hook
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org

Tiedotteesta

Tunnistus:ann15087

Kuvat

ALMA expands its power into global interferometry
ALMA expands its power into global interferometry
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