Final answer:
The Schwarzschild radius of a black hole that is 9 times the mass of the Sun would be 9 times that of the Sun's Schwarzschild radius. This calculation does not require the original star's radius, as the Schwarzschild radius is dependent only on the object's mass.
Step-by-step explanation:
The Schwarzschild radius of a black hole is directly proportional to its mass. This means that if you know the Schwarzschild radius of one black hole, you can calculate the radius for another simply by scaling according to the mass. The radius of a black hole's event horizon can be found using the equation that states the Schwarzschild radius is equal to 3 km times the mass of the black hole in terms of the mass of the Sun. Therefore, a black hole that is 9 times the mass of the Sun would have a Schwarzschild radius that is also 9 times greater than that of the Sun's Schwarzschild radius.
It is crucial to note that the actual physical radius of the star before it becomes a black hole does not affect the Schwarzschild radius, as this is determined solely by the mass of the object once it has undergone gravitational collapse.