What is the velocity of the mass at a time t? you can work this out geometrically with the of the hints, or by differentiating the expression for r' (t) given in the introduction. (figure 2)

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?