Retrograde and prograde motion impact stage, the thickness of a protoplanetary disk is far larger than the size of planetary embryos so collisions are equally likely to come from any direction in three dimensions. This results in the axial tilt of accreted planets ranging from 0 to 180 degrees with any direction as likely as any other with both prograde and retrograde spins equally probable. Therefore, prograde spin with small axial tilt, common for the solar system's terrestrial planets except for Venus, is not common for terrestrial planets in general. The pattern of stars appears fixed in the sky, but that is only because
Solar rotation and quickly at the equator. This profile extends on roughly radial lines through the solar convection zone to the interior. At the tachocline the rotation abruptly changes to solid-body rotation in the solar radiation zone. Solar rotation Solar rotation varies with latitude because the Sun is composed of a gaseous plasma. The reason why different latitudes rotate at different periods is unknown. The rate of surface rotation is observed to be the fastest at the equator (latitude ) and to decrease as latitude increases. The solar rotation period is 24.47 days at the equator and almost 38 days at the