because they are taking about a girl
because the gravitational attraction of our sun for the earth is the centripetal force causing the earth's circular motion around the sun, we can use netwon's law of universal gravitation to find the mass of the sun without ever actually visiting the sun. this is the same technique you would use to determine the mass of cygnus x-1 with a probe. the earth, orbiting the sun, plays the same role as the probe sent to orbit cygnus x-1.
f(force of gravity) = f(centripetal force)