This finding explains the discrepancy between the number of basins detected on the Moon (~40) and the number predicted (~300) by an accretion scenario of planet formation.
Most of the dense material in the dust cloud is attracted strongly and ends up here. The inner four planets (Mercury, Venus, Earth, and Mars) are rocky and have solid surfaces that can be walked on.
An artist’s impression of the two new planets discovered. An inner super-Earth, here seen transiting in front of the orange host-star and an icy giant planet on the periphery of the system.