Prof. Jean-Philippe Beaulieu (Institut d'Astrophysique de Paris, PI of PLANET Project)
Tytul: "PLANET : Detecting a ~5 Earth mass planet by microlensing"
Abstract:
In the favoured core-accretion model of formation of planetary systems, solid planetesimals accumulate to build up planetary cores, which then accrete nebular gas if they are sufficiently massive.
Around M-dwarf stars (the most common stars in our Galaxy), this model favours the formation of Earth-mass to Neptune-mass planets with orbital radii of 1 to 10 AU, which is consistent with the small number of gas giant planets known to orbit M-dwarf host stars. More than 170 extrasolar planets have been discovered with a wide range of masses and orbital periods, but planets of Neptune's mass or less have not hitherto been detected at separations of more than 0.15AU from normal stars. I will first given an introduction to microlensing as a planet hunting method.
Then, I will present the current status of such researches, and in particular the discovery of a 5.5+5.5-2.7 MEARTH planetary companion at a separation of 2.6+1.5-0.6AU from a 0.22+0.21-0.11 MSOLAR M-dwarf star. This detection suggests that such cool, sub-Neptune-mass planets may be more common than gas giant planets, as predicted by the core accretion theory.