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.