A fifth method is direct imaging. This is a difficult technique because it involves searching for a relatively faint planet in the overpowering glare of a bright star—a challenge far more difficult than looking for a firefly in the dazzling brilliance of a
searchlight. This method is most likely to find large planets far from their stars. As of this writing, astronomers have identified a few dozen planets by direct imaging. These planets are all more massive than Jupiter, and most are very far from their star. Some of the planets (including four around a single star) were discovered by large, ground-based telescopes operating in the infrared region of the spectrum with adaptive optics (Figures 7.21 and 7.22).