[juju]

But Undertoad said that the star was getting brighter without getting hotter. So the temperature is remaning the same while the brightness is changing.

I was just suggesting that the brightness might appear to be changing because dust clouds are reflecting or obscuring some of the light. But when the dust clouds move away (move? Would they be in orbit, or just stationary?), more of the star's light is able to get through, thus increasing the brightness.