En duft af ESPRESSO
Her er det enorme diffraktionsgitter, som kommer til at udgøre hjertet i den ultrapræcise spektrograf ESPRESSO. Det bliver næste generation i bestræbelserne for at opdage exoplaneter. Billedet er taget i det rene rum i ESOs hovedkvarter i Garching ved München i Tyskland.
ESOs ingeniører har nu afsluttet det omfattende arbejde med at opliniere gitteret. Fremstilling og opliniering af denne del af spektrografen er et af ESOs hovedbidrag til ESPRESSO-projektet. Gitteret er det største, som nogensinde er blevet monteret ved ESO, og i sin fulde længde er det det et af de længste echellegitre der nogensinde er fremstillet. Det er af samme størrelse - 1,2 x 0,3 m - som det, der sidder i HIRES-spektrografen ved 10 m Keck teleskopet på Hawaii.
Når den endelige opliniering er sket, bliver gitteret fast monteret i en ramme. Alle komponenterne er fremstillet af Zerodur (det er det samme materiale, som bruges til spejlene på VLT), og derefter vil der aldrig være behov for efterjusteringer. Monteringsprincippet er udviklet af ESO, og det virker fint ved tidligere instrumenter.
ESPRESSO skal installeres på ESOs Paranal Observatoium i Chile i 2016. Instrumentet samler lys fra alle de fire teleskoper, som udgør Very Large Telescope. Tilsammen vil de danne et virtuelt teleskop med 16 m diameter. Gitteret deler lyset herfra op i et bredt farvespektrum, som så kan analyseres. Processen er den samme som ved et prisme, men skyldes andre fysiske og optiske love.
ESPRESSO skal afløse HARPS, som er Verdens vigtigste exoplanetinstrument. Med det nye instrument vil astronomerne kunne søge efter jordlignende planeter i den beboelige zone omkring de nærmeste stjerner[1]. Der er også mange andre videnskabelige anvendelser af spektrografen. Det kan for eksempel være eftersøgningen efter variationer i naturkonstanterne til forskellige tider og i forskellige retninger i løbet af Universets historie. Det kan gøres ved at studere meget fjerne kvasarer.
Noter
[1] En planet, som kredser omkring en stjerne, forårsager en lille og regelmæssig variation i den del af stjernens bevægelse, som ligger i synsretningen (det, som kaldes radialhastigheden) i forhold til Jorden. Variationen ses som en "vrikken" i spektret fra stjernen, hvor spektrallinierne flytter sig frem og tilbage hen over en gennemsnitsposition - forårsaget af dopplereffekten. Når planeten bevæger sig væk fra observatøren, giver ændringen af radialhastigheden et skift i stjernespektret hen imod kortere bølgelængder (en blåforskydning), og modsat en rødforskydning, når planeten nærmer sig. Disse små ændringer i stjernens spektrum fylder på detektoren nogle få nanometer, men det kan alligevel måles med ESPRESSO, og kan vise, om der findes planeter i systemet.
Mere information
ESPRESSO (Echelle SPectrograph for Rocky Exoplanet and Stable Spectroscopic Observations) udvikles af et konsortium bestående af ESO og syv yderligere videnskebelige institutioner:
Centro de Astrofísica da Universidade do Porto (Portugal)
- Faculdade de Ciências da Universidade de Lisboa, CAAUL & LOLS (Portugal)
- INAF–Osservatorio Astronomico di Trieste (Italien)
- INAF–Osservatorio Astronomico di Brera (Italien)
- Instituto de Astrofísica de Canarias (Spanien)
- Physikalisches Institut der Universität Bern (Schweiz)
- Université de Genève (Schweiz).
ESO/M. Zamani
Om billedet
| Id: | potw1537a |
| Sprog: | da |
| Type: | Foto |
| Udgivelsesdato: | 14. september 2015 10:00 |
| Størrelse: | 5616 x 3744 px |
Om objektet
| Navn: | ESPRESSO |
| Type: | Unspecified : Technology : Observatory : Instrument |
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