Det bedste billede fra den berømte solformørkelse i 1919
For næsten præcis 100 år siden, forekom en bemærkelsesværdig hændelse: en total solformørkelse. Formørkelsen det år var speciel på mere end een måde. Først og fremmest varede den lidt under syv minutter, så det var den længste totale solformørkelse i mere end 500 år. Desuden brugte astronomerne den til at studere den den gang helt nye generelle relativitetsteori — og det gik godt, og resultaterne var epokegørende.
Einstein offentliggjorde sin generelle relativitetsteori i 1915. Det totale solformørkelse i 1919 var den perfekte lejlighed til at afprøve teorien eksperimentelt ved at undersøg om, og hvordan Solens enorme tyngdekraft afbøjer og spreder det lys, som kommer ind fra fjernere stjerner, sådan som Einsteins teori forudsiger. I et kort øjeblik under formørkelsen vil Månen spærre for Solens lys, og dermed bliver nogle af de stjerner synlige, som befinder sig tæt ved synslinien til Solen på det givne tidspunkt. Det er stjerner, som ellers ikke er synlige i dagtimerne på den tid af året. Positionerne under formørkelsen for disse stjerner blev målt, og sammenlignet med deres positioner på den normale nattehimmel, hvor Solen ikke forstyrrer. Dermed var det muligt at se, om lyset fra stjernerne blev afbøjet ved den tætte passage forbi Solen.
Tre astronomer - Arthur Eddington, Frank Watson Dyson, og Andrew Crommelin — havde nøgleroller i eksperimentet i 1919. Eddington og Crommelin rejste ud til steder, hvor formørkelsen ville være total: Eddington til den vestafrikanske ø Principe og Crommelin til den brazilianske by Sobral. Dyson koordinerede forsøget hjemme fra England.
Både Eddington og Crommelin afbildede formørkelsen med den teknologi, som var til rådighed i den periode: fotografiske glasplader. Desværre er de originale glasplader fra 1919 expeditionen (hvoraf den ene blev brugt i Dysons originale videnskabelige artikel) gået tabt, men heldigvis blev der lavet kopier af en af pladerne, og de blev sendt ud til observatorier over hele Verden, så forskere med deres egne øjne overalt kunne se beviserne, som støttede relativiteten. En kopi af en plade fra Sobral blev sendt til Landessternwarte Heidelberg-Königstuhl,og her har man for nyligt scannet den, som et bidrag til projektet Heidelberg Digitized Astronomical Plates (HDAP) [1].
Billedet her her helt sikkert det fra formørkelsen i 1919, som har højest opløsning, og det er et resultat af at bruge moderne billedbehandlingsteknikker - herunder billedrestaurering, støjfjernelse og rensning for fejl (der kan findes en version uden tekst her). Man ser utrolige detaljer i Solens korona og en enorm prominens, som strækker sig ud fra den overste højre del af Solen. Desuden ser man stjerner i stjernebilledet Taurus (Tyren), som er dem, der blev brugt til at bekræfte forudsigelserne i den generelle relativitetsteori [2].
Notes
[1] HDAP får støtte fra bevillingen No. 00.071.2005 fra Klaus Tschira Foundation. Her viser vi det originale højopløsningsscan før den digitale bearbejdning, af historiske grunde.
[2] Dysons originale artikel konkluderer med den afgørende graf på side 332 sagen, ved at plotte stjernernes forskydning under formørkelsen som funktion af deres vinkelafstand fra Solskivens centrum. Det viser en klar sammenhæng (den rette linie): Stjernerne tæt ved retningen til Solen får deres lys afbøjet mere end de, som er længere væk, og værdien er nogenlunde den, som er forudsagt af den generelle relativitetsteori (og det er det dobbelte af, hvad klassisk Newtonsk fysik forudsiger - den punkterede linie).
Kilde:ESO/Landessternwarte Heidelberg-Königstuhl/F. W. Dyson, A. S. Eddington, & C. Davidson
Om billedet
| Id: | potw1926a |
| Sprog: | da |
| Type: | Planetarisk |
| Udgivelsesdato: | 1. juli 2019 06:00 |
| Størrelse: | 23800 x 14191 px |
Om objektet
Billedformater
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