Le lune ghiacciate di Giove
Questa immagine della settimana mostra due lune di Giove, le ghiacciate Ganimede ed Europa, che sono state fotografate nell'infrarosso grazie allo strumento SPHERE del Very Large Telescope dell'ESO. Mentre Europa è abbastanza simile alla nostra Luna, Ganimede è la luna più grande dell'intero Sistema Solare: è persino più grande del pianeta Mercurio!
Le loro orbite intorno a Giove sono leggermente ellittiche, quindi si avvicinano e si allontanano dal pianeta durante la loro orbita. Questo fa sì che le lune vengano stirate e schiacciate dall'attrazione gravitazionale di Giove a intervalli periodici. Questo crea un calore da attrito che riscalda l'interno delle lune, rendendole geologicamente attive. In particolare, è probabile che Europa abbia pennacchi e geyser attivi che eruttano dagli oceani di acqua liquida sotto la spessa coltre di ghiaccio che ne costituisce la superficie.
Grazie a queste nuove immagini e agli spettri, pubblicati in due studi di Oliver King e Leigh N. Fletcher dell'Università di Leicester nel Regno Unito, è stato possibile stimare le abbondanze di specie chimiche sulle superfici marmoree di queste lune. Essi hanno scoperto che le regioni luminose di Ganimede sono costituite principalmente da acqua sotto forma di ghiaccio, con accenni a vari sali, e che si sono formate più di recente rispetto alle macchie scure più vecchie, la cui composizione rimane ancora un mistero per gli astronomi.
L'osservazione di queste lune con i telescopi a terra è impegnativa, perché sembrano piccole come una moneta da 1 euro viste a 3-5 km di distanza. L'atmosfera terrestre offuscherebbe completamente queste immagini, ma il sistema di ottica adattiva di SPHERE corregge queste distorsioni, fornendo immagini molto nitide con dettagli fino a 150 km.
Link:
- Immagini individuali di Europa e Ganimede (1, 2, 3 & 4).
Crediti:ESO/King & Fletcher. Jupiter background image: NASA, ESA, A. Simon (Goddard Space Flight Center), and M. H. Wong (University of California, Berkeley) and the OPAL team.
A proposito dell'immagine
| Identificazione: | potw2241a |
| Lingua: | it |
| Tipo: | Collage |
| Data di pubblicazione: | Lunedì 10 Ottobre 2022 06:00 |
| Dimensione: | 6750 x 4108 px |
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