Exoplanets are planets that orbit stars outside our own solar system. Astronomers detect them indirectly, often by observing a star's slight dimming. This dimming occurs when a planet passes in front of its star from our viewpoint. Thousands of exoplanets have been confirmed since the first discovery in the 1990s. Some appear to orbit within a star's habitable zone, where liquid water could exist. According to the passage, how do astronomers typically detect exoplanets?
