Testluv wrote:received a pm.

As Ron says, other posters have done a good job. Let's put some numbers to this question. First, we need to understand that the TOTAL amount of light emitted by the comet never changes.

So:

Before: 1 unit of mass--> 60 units of light. Let's say that TOTAL light is 120 units. Then, the previous estimate of the comet's mass is 120/60 = 2 units of mass.

Now: 1 unit of mass--> 1 unit of light (60 times less). The TOTAL light is still 120 units. Then, the revised estimate of the comet's mass is 120/1 = 120 units of mass.

Therefore, the previous estimate of the comet's mass (based on brightness) is too low, and choice B is correct.