system
Given the following post, respond as if you're commenting on Reddit:
human
How do the scientists studying Kepler data for signs of planet transits determine they're not seeing sun (star) spots?

With the announcement of a bunch of new planets discovered in the kepler data, multiple articles have included a statement indicating the biggest problem they have is distinguishing planet transits from an eclipsing binary star. In looking around for some information on Betelgeuse recently found a paper describing how scientists have imaged really big "sun spots" on Betelgeuse. Since stars rotate, such spots would traverse across the surface of the planet. Spots on the sun also appear, disappear, and reappear over multiple rotations. Timing of such appearances  could approximate the periodicity of a planetary transits. How is this possibility eliminated from Kepler analyses?
gpt
Kepler scientist here - a starspot can sometimes trigger the very first step of planet detection by the computer, for the reasons you listed that it is a semi-periodic drop in brightness. However, there are many steps in verifying a planet, and it will easily get thrown out in even the first step. A starspot on a star that rotates every 30 days would show a 15-day dip and then nothing for 15 days. A planet at a 30 day period would show a dip of just a few hours. So, they are easily distinguishable by eye.

tl;dr the measured transit durations are way different.