Please help me with this astronomy problem. I am supposed to calculate the smallest planet that is detectable with the transit method, given a signal to noise ratio and a star's radius: Suppose the star is seen at its distance D with a signal to noise ratio of S/N = 10^4. This means that in the light curve for the star (i.e. ﬂux vs. time), the ‘noise’ is 1/10000 the mean of the star’s ﬂux). What is the smallest planet that is detectable? (Hint: assume that the noise has a standard deviation σ and that detection of the transit requires at least a 3σ dip in the ﬂux.) Consider a star exactly like the Sun and evaluate your expression in kilometers by using the known radius of the Sun (5*10^5 km). Any help is appreciated!