Final answer:
Astronomers use indirect detection techniques such as the transit and Doppler methods to reveal things like rogue planets that can't be seen with our eyes alone.
Step-by-step explanation:
In order to reveal things that we can't see with our eyes alone, such as rogue planets, astronomers use indirect detection techniques. These techniques observe the effects that planets have on the stars they orbit instead of directly seeing the planets themselves.
One example of an indirect detection technique is the transit method. When a planet passes in front of its star, it causes a temporary decrease in the brightness of the star. Another technique is the Doppler method, where the gravitational tug of a planet causes a small wobble in its star's motion.
While a few exoplanets have been imaged directly, most of them are detected using these indirect techniques because they are generally lost in the glare of their parent stars.