You’re looking at the first map ever made of a planet around another star. Of course, even the next generation of astronomical instrumentation is orders of magnitude away from achieving the resolution needed to actually produce an image of a planet that far away. But Knutson et al. (2007) took a different approach - they let the planet resolve itself. Using the Spitzer Space Telescope, they took about 300,000 consecutive images of the star HD 189733 as its primary planet (a Hot Jupiter) slowly completed its orbit. With each image, the planet slowly rotated before the camera. They then calculated the brightness of the star+planet system as a function of the planet’s rotation angle (longitude), shown in part b) of the figure above. With that information, they constructed a map of the brightness distribution on the planet surface (part a). This map provided some of the most valuable constraints to date on the temperature variation across a planet’s surface from day to night, and has led to important consequences in our understanding of the atmospheres of Hot Jupiters.