The cold worlds absent in our Solar System

The standard core accretion planet formation theory predicts numerous "failed gas giant cores" in the wide orbits (>~ 1 AU), with masses less than about 10 Earth mass, but such planets are absent in our solar system. The gravitational microlensing technique is currently the only method that can probe low-mass wide-orbit planets, but before 2020 only a few such planets were detected, indicating a paucity of "failed gas giant cores". Since 2020, I have been leading two projects to capture "failed gas giant cores", which successfully detected about 10 planets smaller than the detection record by 2020, suggesting that "failed gas giant cores" are more common than previously believed.