Allah (swt) mentions the planets that some people worshiped. Since, on this day balance of the planets is disturbed, each planet leaves its orbit which they used to move around. The word planet indicates that it takes its light from another object, contrary to the stars. For the planet takes its light from the sun, so that when it goes down, we will not see the planets which proves to us that each planet will end up in decline.
انتَثَرَتْ (scattered): scattering is the opposite of gathering. To scatter is to throw things on the floor irregularly. As such, the scattering of the planets is the dispense of their form of gathering in their positions or the exiting of the planets out of their orbits so they appear in disorder in space due to gravity disturbance upon which the universe was built.