> Astronomers use sun spots, travelling across the surface, and these only dim its brightness by much less than 1%. How do they know they are sun spots and not

> Astronomers use sun spots, travelling across the surface, and these only dim its brightness by much less than 1%. How do they know they are sun spots and not a very small planets? I'd assume planets have a more regular schedule, but unless you watch a star for years (Julian), how can you tell?