A random person put the answer for you
They are different measurements
<span>That the mass is far lesser
and distributed mistakenly, as compared to what the orbits of stars declare it
should be. Stars orbit more rapidly than the mass would predict, particularly
out toward the galactic edge. This means that there is more mass than has been
measured, and that it is spread out in a huge cloud around the galaxy. This is
one of the reasons why scientists believe that dark matter exists.</span>
