Self-assessment Are the following statements true or false? –Most exoplanets were detected indirectly. True False –The bright objects in the sky are never exoplanets. True False –The bright objects in the sky are never planets. True False –The centre of gravity of a star-planet system is closer to the planet than to the star. True False –Exoplanets are spherical. True False –A planet which passes in front of its star causes a mini-eclipse ? called transit. True False –Some exoplanets were ejected from their planetary system. True False –There are no planets around binary stars. True False –Most stars are surrounded by planets. True False –Most stars are in multiple star systems. True False –Stars do not emit infrared light. True False –Oxygen and hydrogen are 2 of the 3 most numerous atoms in the Universe. True False –Liquid water always contains life. True False –Traces of life have been found on Mars. True False –Water is present throughout the Universe. True False –Liquid water is present throughout the Universe. True False –Exoplanets covered with liquid water have been discovered. True False –Molten metal exoplanets have been discovered. True False –Exoplanets covered with forests have been discovered. True False –Exoplanets with clouds have been discovered. True False –There are many exoplanets with elliptical orbits. True False –Many exoplanets have migrated far from the place they were formed. True False Which is the correct answer? (several possible answers) –Imaging more easily detects the exoplanets close to their star? Yes, because the exoplanet is better illuminated by the star. No, because the detector is dazzled by the light from the star. –There could be life in the Jupiter system? No, because Jupiter is not in the Sun’s habitable zone. Yes, because there is probably liquid water on Europa and Ganymede. No, it is too cold for life to develop. –The spherical shape of a planet is caused by: the presence of liquid water. its speed of rotation. gravity. –There are exoplanets: only around stars. only around stars and brown dwarfs ? around stars, brown dwarfs ? and star residues. –In a system with a planet and a star: the planet orbits around the star. the star and the planet orbit around the centre of gravity. the star orbits around the planet. –The mass of the most numerous exoplanets is: one mass of Mars. five masses of Jupiter. ten masses of Earth. –Why do we look for liquid water when searching for life? In a liquid, the molecules are close to each other. Liquid water is rare in the Universe. A liquid medium activates the chemical reactions. –Which technique cannot be used on satellite ? ? Radial velocities ? . Astrometry ? . Transits.