WASP-12b is one of the darkest known exoplanets. The planet’s day side eats light rather than reflecting it into space. This weird planet, which is twice the size of Jupiter, has the unique ability to trap at least 94% of the visible starlight falling into its atmosphere. The day side hoards all the visible light because it always faces its star. The temperature of its atmosphere is a soaring 4,600°C (8,312°F). This oddball exoplanet is one of a class of so-called “hot Jupiters” that orbit very close to their host star and are heated to enormous temperatures.
The planet orbits so close to its host that it has fixed day and night sides. WASP-12b completes an orbit once a day. The night side is much cooler, with temperatures roughly 2,200°C (3,992°F), which allows water vapor and clouds to form. A swirl of material from the planet’s super-heated atmosphere spills onto its star.