Voyage to the Centre of the Stars
Launched last year, the CoRoT satellite has just delivered its first data. Its mission: to allow studies of the centre of stars to take place and to discover new planets beyond our solar system and, why not, other habitable earth like worlds.
It was in the hope of filling in this gap that the French Space Agency (CNES) launched the CoRoT project at the beginning of the 1990s (COnvection ROtation and planetary Transits). The agency was very quickly joined in the adventure by numerous international partners, including Belgium, Germany, Austria, Spain, Brazil and the European Space Agency (ESA). The project was at that time entirely devoted to observational asteroseismology. What is involved? A star resembles a beating heart. Its surface is permanently animated by a vibratory movement which depends on what the star has in its guts, in the same way that earthquakes tell us about the physical conditions which dominate the interior of our planet. Thereby, observing the undulations of the stars' surfaces opens the door to stellar physics.
A tiny variationOn the observational level, a star’s vibrations are translated into a periodic variation in its brightness. Nevertheless, the amplitude of this variable luminosity is so minimal that measurements must be precise down to the millionth. The only way to achieve such precision is to collect a maximum of the light emanating from the stars that are to be observed and thus to increase the length of time they are under continuous observation. This objective is difficult to carry out with a telescope fixed on the ground as the data, already polluted by the atmosphere, are cut up into fragments by the day-night cycle and the weather. Alternatively, periods of observation lasting up to 150 days without interruption can be envisaged if a spatial telescope is used. The CoRoT mission has at its disposal such a telescope, launched from the Baikonur facility on the 27th December, 2006, and placed in orbit at close to 900km above our heads. On the agenda: two exploratory phases of 30 to 60 days each, The variations in brightness to be measured being minimal, it is important not only that the telescope has its back turned permanently to the Sun, but also that its detectors be protected from all light pollution, originating mainly from the Earth. The relative proximity of CoRoT to our planet and the lengthy duration of continuous observation that it will carry out have offered real technological challenges to the satellite's designers. These challenges were nailed down by the Liège Space Center, which developed and perfected the optic baffle which offers the instruments optimal protection. |
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© 2007 ULi�ge
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