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De VS willen Europa inhalen in de zoektocht naar exo-aardes

Geplaatst op 30-03-2009 om 23u08 door Stefan De Decker - 2655 keer gelezen
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Europese en Amerikaans onderzoekers zijn in een vriendschappelijke concurrentiestrijd verwikkeld om zo veel mogelijk exoplaneten te ontdekken, de kleinste exoplaneet, de exoplaneet met het meeste overeenkomst met onze aarde enz…

Tot op heden hebben de Europeanen een kleine voorsprong, vooral in het vinden van kleinere of minder zware exoplaneten. Dit is mede te danken aan de Corot missie die onlangs de kleinste exoplaneet tot nu toe vond maar ook de super gevoelige HARPS (High Accuracy Radial velocity Planet Searcher) spectrograaf die gekoppeld is aan ESO’s 3.6 meter telescoop in Chili. Het licht komt via optische glasvezelkabels toe in het supergekoelde instrument.

De variatie in snelheid waarmeer een ster zich naar ons toe of van ons weg beweegt wordt beïnvloed door een planeet die rond die ster draait. Hoe kleiner de planeet hoe kleiner het effect dat wordt uitgeoefend op de ster. Jupiter bijvoorbeeld verandert de snelheid van de zon met 12 meter per seconde. De aarde is veel lichter en kan de zon slechts 10 cm per seconde doen veranderen van snelheid. Indien de aarde veel dichter rond de zon zou draaien zou het effect dat ze op de zon uitoefent wel groter zijn bv. 0.5 meter per seconde.

Het licht van de ster zal ons bereiken in een iets kortere golflengte (blauwer licht) wanneer de ster naar ons toe beweegt en met een langere golflengte (roder licht) wanneer de ster zich verder verwijderd. HARPS kan dit effect meten met een nauwkeurigheid van minder dan 1 meter per seconde en dat is absolute wereldtop.

De Amerikanen willen nu hun achterstand goedmaken. Het FINDS project staat voor (Fiber-optic Improved Next generation Doppler Search for Exo-Earths) en het is een nieuw optisch systeem dat geïnstalleerd zal worden op de 3 meter telescoop van het Lick Observatorium in Californië. In een later stadium zou het instrument geïnstalleerd kunnen worden aan een van de Keck telescopen in Hawaï.

De Amerikanen verwachten veel van de onlangs gelanceerde Kepler missie, die gevoeliger is dan de Europese Corot missie en bovendien meerder jaren ononderbroken naar hetzelfde sterrenveld zal kunnen kijken in tegenstelling tot Corot. Kepler zal een groot aantal kandidaat planeten opleveren die d.m.v. onderzoek met een spectrograaf al dan niet als echte planeten weerhouden zullen worden.

Het nieuw Amerikaanse systeem is 2-ledig: eerst wordt het licht van de telescoop gebundeld en zonder verlies door de optische kabels gestuurd die het binnenkomende verstrooien en zorgen voor een meer uniforme (gelijkmatige) stroom licht naar het instrument. Ten tweede is er de adaptieve optiek. Deze laatste zorgt voor het wegfilteren van invloeden van de atmosfeer om de “ruis” in het licht te minimaliseren en voorkomt ook dat er kostbaar licht verloren gaat.

Met deze nieuwe technologie zal de 3 meter Lick telescoop binnenkort een gevoeligheid van 1 meter per seconde kunnen bereiken. Met de veel grotere 10 meter Keck telescoop is de hoeveelheid licht dat naar het instrument kan worden gestuurd hoger en zou een nauwkeurigheid van 0.5 meter per seconde kunnen worden bereikt en zouden komen exoaardes stilaan binnen ons bereik komen.

Bron: The Planetary Society

Gerelateerde berichten

Lees ook: Wetenschappers ontdekken mogelijk super-aarde
Lees ook: Superaarde ontdekt met atmosfeer en mogelijk oceanen
Lees ook: Aardachtige planeten niet zo zeldzaam
Lees ook: Planetenvorming waargenomen
Lees ook: Exoplaneet onder de loep
Lees ook: Planeten rond dubbelsterren

Bekijk alle berichten uit deze categorie.

Er hebben al 2 mensen een reactie achtergelaten

Bert Geplaatst op 31-03-2009 om 10u36 - Quote

Die 'concurrentiestrijd' is zeker een positieve evolutie in de zoektocht naar aardachtige planeten.

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