 There is disagreement as to whether it is and has always been a hot Neptune in mass (Lammer), or if it could have developed from a gas giant, losing most of its mass on the way (Baraffe).If an eroded gas giant, the sun would have boiled the planet from a larger protoplanet, of 20 Earth masses up to half Jupiter's mass.If the latter, its current radius could be as high as 0.6 Jupiter.