From the March 2011 issue

How does one differentiate between an exoplanet orbiting in front of a distant sun and a large starspot traveling across that star’s disk?

Melvyn Goldberg, Toronto, Canada
By | Published: March 28, 2011 | Last updated on May 18, 2023
The light curve of an exoplanet transiting its star (top) is different from that of a starspot traversing a star’s disk, so astronomers can tell the two signals apart. Astronomy: Roen Kelly

Thus we can distinguish a transit by the short duration of the dip. … so the dip of a transit is slightly “U-shaped.” The shape of the starspot dip has gentle sides and looks more “V-shaped.”