A planet as hot as the sun
The Kepler space telescope has in its sights two small rocky planets which were detected in another solar system. Could they be copies of our Earth orbiting their sun? Not really, because the planets show a surface temperature of more than 6000°C and their star, which is already in a late stage of evolution, has ejected half of it its mass into interstellar space. The story was published in the journal Nature.
The detection of an exoplanet is one thing but characterizing it is another: is it large like Jupiter or small like our Earth? Does it gravitate near its star or to the outer edges of the planetary system? Is it gaseous or rocky? Characterizing an exoplanet necessitates a minimal knowledge of its star. There is a kind of degeneration to be drawn between the parameters of the star and those of the planet. Asteroseismology is the only doorway to an understanding of the physics at work in the cores of stars (see article entitled “Journey to the heart of the stars”). This science is therefore the indispensable tool for characterizing exoplanets. What does it involve? The majority of stars vibrate just like a heart beats. These vibrations inside the star manifest themselves on the surface by variations in luminosity which, when interpreted, constitute a veritable mine of information about the nuclear reactions that occur at the heart of the star, its chemical composition, its mass, etc.
(1) S. Charpinet, G. Fontaine, P. Brassard, E.M. Green, V. Van Grootel, S.K. Randall, R. Silvotti, A.S. Baran, R.H. Ostensen, S.D. Kawaler & J.H. Telting, A compact system of small planets around a former red-giant star; Nature, December 2011