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COROT découvre sa première exoplanète et prend les scientifiques par surprise   This is an artist’s impression of a Jupiter-sized planet passing in front of its parent star. Such events are called transits. When the planet transits the star, the star’s apparent brightness drops by a few percent for a short period. Through this technique, astronomers can search for planets across the galaxy by measuring periodic changes in a star’s luminosity.
The first class of exoplanets found by this technique are the so-called “hot Jupiters,” which are so close to their stars they complete an orbit within days, or even hours.  This image shows the signature of the presence of a planet orbiting a star. The intensity of light coming from the star is represented on the y-axis whereas the x-axis shows the phase, or the revolution of the planet around the star. The amount of light from the star reaching COROT decreases each time the planet passes in front of the star itself. This is when the drop is registered. This was the first planet detected by COROT since the beginning of its mission. This light curve is part of a data set obtained between February and April 2007. The planet is a very hot gas giant, of radius equal to 1.78 times that of Jupiter. The planet takes 1.5 days to revolve around the star.
Coordinated spectroscopic observations from the ground have allowed to determine that the mass of the planet is about 1.3 times that of Jupiter. The parent star is a yellow dwarf star similar to our Sun. It is located in the direction of the constellation Unicorn (Monocerus), roughly 1 500 light years from us.  As the planet passes in front of its parent star, the brightness of the star decreases.
Figure based on image by Hans Deeg, from '
Transits of extrasolar planets'.  This image shows the light curve emitted by a binary star system as seen by COROT. The crests show light emitted by both stars. However, when one star eclipses the other, the troughs are created due to a decrease in the amount of light reaching COROT. The periodicity is seen since the stars are revolving around each other with a fixed period. The light curve was obtained by COROT during observations performed between February and April 2007.
This high quality of this light curve is due to the continuity of the observations and their high accuracy. Release date: 4 mai 2007 |