Astronomen entdecken ein Sonnensystem, das ihrer Meinung nach nicht möglich sein sollte

This system is not impossible but it does break standard expectations.

The important point to note is the outer rocky planet sitting beyond two gas-rich ones. In classical disk models that should not happen obviously, because gas giants form efficiently beyond the snow line before the gas disk dissipates. The authors tested migration, collisions, and atmospheric stripping and none of it worked.

Best explanation is gas-depleted, inside-out formation inner planets formed first while the disk was gas-ric; the outer rocky planet formed later when most of the gas was already gone so it would never became a gas giant. Thats very unusual but physically plausible especially around red dwarfs