Determinar la corriente que debe circular por un conductor para que la inducción magnética en un punto situado perpendicularmente a 20 cm de aquel sea de 500 micro T

The seven sisters, seven stars located more than 400 light-years away in the taurus constellation can be seen here with venus and another constellation, orion. the seven stars stay grouped together but seem to move, like the planet venus. why do stars seem to move like planets in the night sky?